Crystals

15 pages, 2434 KB

Open AccessEditor’s ChoiceArticle

Linear and Nonlinear Dynamics of Crystals with B2 (CsCl) Structure

by Dina U. Abdullina, Sergey V. Dmitriev, Ilya S. Sugonyako, Arseny M. Kazakov and Elena A. Korznikova

Crystals 2026, 16(5), 286; https://doi.org/10.3390/cryst16050286 - 25 Apr 2026

Cited by 1 | Viewed by 741

Abstract

This study investigates the phenomenon of supratransmission in three-dimensional crystals with a B2 (CsCl) structure, employing classical molecular dynamics with β-Fermi–Pasta–Ulam–Tsingou potentials up to fourth-nearest neighbors. We analyze energy transfer from a harmonically driven surface into the crystal bulk across various frequency regimes [...] Read more.

This study investigates the phenomenon of supratransmission in three-dimensional crystals with a B2 (CsCl) structure, employing classical molecular dynamics with β-Fermi–Pasta–Ulam–Tsingou potentials up to fourth-nearest neighbors. We analyze energy transfer from a harmonically driven surface into the crystal bulk across various frequency regimes relative to the phonon spectrum. While low-amplitude excitation results in energy transmission only within the phononic bands, high-amplitude driving triggers supratransmission in the phononic gap and above the optical band. Our results demonstrate that in these nonlinear regimes, energy is transported not by linear phonon waves but by discrete breathers (DBs) emitted quasi-periodically from the surface. A key finding is the distinct sublattice selectivity of these excitations: gap DBs propagate primarily along the heavy atom sublattice, whereas above-spectrum DBs travel along the light atom sublattice. We quantify the velocities and oscillation periods of these localized modes, revealing their critical role in bypassing linear spectral restrictions. These findings provide new insights into nonlinear energy transport in binary alloys and suggest potential applications for controlling heat flow and signal processing in crystals. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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27 pages, 3527 KB

Open AccessEditor’s ChoiceArticle

Molecular Dynamics of Ice Ih Impacts on FCC Metals: Interfacial Melting and an Anti-Icing Index of Merit

by Alexandre Brailovski, Ali Beydoun, André Guerra, Alejandro D. Rey and Phillip Servio

Crystals 2026, 16(4), 276; https://doi.org/10.3390/cryst16040276 - 19 Apr 2026

Viewed by 1508

Abstract

Ice adhesion on exposed structures remains a major operational challenge, motivating the search for passive, material-based anti-icing strategies. Molecular dynamics offers a controlled way to investigate ice–surface interactions beyond the limits of experimental setups. In this work, we develop a simulation framework to [...] Read more.

Ice adhesion on exposed structures remains a major operational challenge, motivating the search for passive, material-based anti-icing strategies. Molecular dynamics offers a controlled way to investigate ice–surface interactions beyond the limits of experimental setups. In this work, we develop a simulation framework to model the impact of solid hexagonal ice droplets on metallic substrates. Ice impacts are simulated across a range of velocities (10–120 m/s), temperatures (120–250 K), and face-centred cubic surface materials (gold, copper, silver, aluminum, and nickel). Using LAMMPS, mW water force-field, EAM/Alloy metal potentials, and Lennard-Jones water–surface interactions, we quantify phase evolution through angular order parameter and quasi-liquid layer measurements, complemented by the CHILL+ algorithm in OVITO. By isolating all external factors, we show that melting increases with velocity and temperature and correlates with substrate properties: metals with high thermal diffusivity and low Young’s modulus tend to decrease post-collision ice melting. The ratio of the former to the latter, a derived index of merit Υ, significantly correlates with melting percentage and identifies silver as the most effective anti-ice material examined. Statistical analyses strongly suggest that these surface properties influence interfacial melting, supporting the use of this modelling framework for screening and designing anti-icing materials. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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17 pages, 7703 KB

Open AccessEditor’s ChoiceArticle

Characterization of the Intermetallic Phases in Ti/Zn and TiAlV/Zn Composite Materials

by Veronika Balejová, Martin Suláni, Alena Michalcová, Jan Blažek and Dalibor Vojtěch

Crystals 2026, 16(4), 275; https://doi.org/10.3390/cryst16040275 - 18 Apr 2026

Cited by 1 | Viewed by 933

Abstract

Composite materials with Ti or Ti alloy reinforcement in a Zn matrix are new, promising materials with potential applications in implantology. Infiltrating zinc into the porous titanium reinforcement of a designed implant could improve its osseointegration. In this field, it is important to [...] Read more.

Composite materials with Ti or Ti alloy reinforcement in a Zn matrix are new, promising materials with potential applications in implantology. Infiltrating zinc into the porous titanium reinforcement of a designed implant could improve its osseointegration. In this field, it is important to avoid the formation of brittle intermetallics; therefore, understanding their growth is fundamental. This work focuses on characterizing the Ti-Zn intermetallic phases at the interface of the TiAlV/Zn and Ti/Zn composites. Samples were prepared by immersing the Ti-6Al-4V or Ti bulk material in zinc melt at various temperatures. After various dwell times, the samples (pieces of Ti-6Al-4V or Ti in the molten zinc) were removed from the furnace and cooled in air. The sequence of evolution of intermetallic phases was observed to be dependent on dwell time at selected temperatures. The influences of surface treatment methods on the boundary structure were also tested. Full article

(This article belongs to the Special Issue Processing–Structure–Property Relationships in Next-Generation Titanium Alloys)

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18 pages, 835 KB

Open AccessEditor’s ChoiceArticle

Entropy-Driven Isosymmetric Phase Transition in L-Serine Under Pressure: A Periodic DFT Study

by Anna Maria Mazurek, Monika Franczak-Rogowska and Łukasz Szeleszczuk

Crystals 2026, 16(4), 266; https://doi.org/10.3390/cryst16040266 - 16 Apr 2026

Viewed by 565

Abstract

Understanding pressure-induced isosymmetric phase transitions in molecular crystals requires consideration of both structural and thermodynamic factors, particularly in hydrogen-bonded systems. In this work, periodic density functional theory (DFT) calculations were employed to investigate the pressure-dependent behavior of L-serine and to elucidate the origin [...] Read more.

Understanding pressure-induced isosymmetric phase transitions in molecular crystals requires consideration of both structural and thermodynamic factors, particularly in hydrogen-bonded systems. In this work, periodic density functional theory (DFT) calculations were employed to investigate the pressure-dependent behavior of L-serine and to elucidate the origin of its experimentally observed phase transition between Phase I and Phase IV. Geometry optimizations performed at ambient pressure and 8.8 GPa reproduce the compression of the crystal lattice and the pressure-driven stabilization of Phase IV. However, no spontaneous reorientation of the hydroxyl groups is observed, indicating that the transition is not accessible within a purely static framework. To further explore the stability of the system, a series of modified crystal structures with different hydroxyl group orientations was generated and analyzed, revealing a complex energy landscape at ambient conditions that becomes significantly simplified under compression. Phonon calculations within the quasi-harmonic approximation demonstrate that the experimentally observed Phase I structure is not stabilized by enthalpy but by vibrational entropy, whose contribution increases with temperature. These results show that the phase transition in L-serine is governed by an interplay between lattice energy, hydrogen-bond rearrangement, and vibrational effects, and highlight that an accurate description of polymorphic stability in such systems requires inclusion of both static and dynamic contributions. Full article

(This article belongs to the Special Issue Advances in Pharmaceutical Crystals: Numerical Simulations and Experimental Investigations)

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33 pages, 2679 KB

Open AccessEditor’s ChoiceReview

X-Ray Characterization of Semiconductor Materials and Advanced Packaging: A Perspective on Multidimensional Structural Analysis

by Yumeng Jiang, Zhenwei Zhang, Zhongyi An, Xinyu Pan, Xinmin Shi, Ruonan Wang, Jiajian Li, Chengzhi Chen, Zhiqiang Cao, Yong Xu, Jiaqi Wei, Xueying Zhang and Yi Peng

Crystals 2026, 16(4), 265; https://doi.org/10.3390/cryst16040265 - 14 Apr 2026

Viewed by 3003

Abstract

X-ray techniques provide powerful, non-destructive tools for structural characterization in semiconductor manufacturing and advanced packaging. Their strong penetration capability and sensitivity to multiple contrast mechanisms enable the investigation of lattice structure, strain, defects, interfaces, and elemental distribution across a wide range of length [...] Read more.

X-ray techniques provide powerful, non-destructive tools for structural characterization in semiconductor manufacturing and advanced packaging. Their strong penetration capability and sensitivity to multiple contrast mechanisms enable the investigation of lattice structure, strain, defects, interfaces, and elemental distribution across a wide range of length scales. As semiconductor devices evolve toward three-dimensional architectures and heterogeneous integration, there is an increasing demand for characterization approaches capable of probing complex, buried, and multi-scale structures in a consistent manner. In this review, we present a systematic overview of X-ray characterization techniques for advanced semiconductor systems, including diffraction-based methods, small-angle scattering, computed tomography, X-ray fluorescence, and spectroscopic approaches. These techniques are discussed in terms of the type of structural, morphological, and compositional information they provide, their applicable length scales, and their strengths and limitations in addressing key challenges such as thin films, high-aspect-ratio structures, buried interfaces, and full wafers. Particular attention is given to the complementary nature of different X-ray modalities and their roles in addressing practical metrology problems. The limitations associated with resolution, model dependence, and data interpretation are also outlined. Finally, emerging opportunities in laboratory X-ray sources, synchrotron-based methods, and integrated characterization strategies are briefly discussed. This review aims to provide a unified perspective for understanding and integrating X-ray techniques, offering insights into their roles in addressing the growing complexity of next-generation semiconductor devices. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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10 pages, 5251 KB

Open AccessEditor’s ChoiceArticle

Temperature-Dependent Sn Incorporation and Defect Formation in Pseudomorphic SiSn Layers on Si (001) via Molecular Beam Epitaxy

by Diandian Zhang, Nirosh M. Eldose, Dinesh Baral, Hryhorii Stanchu, Mourad Benamara, Wei Du, Gregory J. Salamo and Shui-Qing Yu

Crystals 2026, 16(4), 262; https://doi.org/10.3390/cryst16040262 - 13 Apr 2026

Viewed by 825

Abstract

SiSn alloys have attracted growing interest for group-IV bandgap engineering, although their epitaxial growth remains challenging due to the extremely low equilibrium solubility of Sn in Si. In this work, fully strained (pseudomorphic) SiSn epitaxial layers were grown on Si (001) substrates by [...] Read more.

SiSn alloys have attracted growing interest for group-IV bandgap engineering, although their epitaxial growth remains challenging due to the extremely low equilibrium solubility of Sn in Si. In this work, fully strained (pseudomorphic) SiSn epitaxial layers were grown on Si (001) substrates by means of molecular beam epitaxy. A systematic investigation reveals a strong inverse correlation between growth temperature and Sn incorporation efficiency. Despite a constant Sn flux, the incorporated Sn composition decreases from 5.5% to 3.2% as the growth temperature increases, indicating a pronounced temperature dependence of Sn incorporation. Reflection high-energy electron diffraction indicates a gradual transition of the growth from two-dimensional to three-dimensional with increasing film thickness. Structural characterization by means of X-ray diffraction, atomic force microscopy, and transmission electron microscopy confirms the pseudomorphic growth and smooth surface morphology and reveals twins and stacking faults near the surface region. These results establish a quantitative reference for SiSn growth kinetics and provide guidance for future studies of SiSn and SiGeSn alloys in silicon-compatible electronic and optoelectronic applications. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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22 pages, 4554 KB

Open AccessEditor’s ChoiceArticle

Experimental and Numerical Investigation on the Formation Mechanism of Freckle Defects in a Novel Third-Generation Nickel-Based Single Crystal Superalloy Turbine Blade

by Xiaoshan Liu, Anping Long, Haijie Zhang, Dexin Ma, Min Song, Menghuai Wu and Jianzheng Guo

Crystals 2026, 16(4), 245; https://doi.org/10.3390/cryst16040245 - 6 Apr 2026

Viewed by 1133

Abstract

This paper investigates the formation mechanism and key influencing factors of freckle defects that arise during the directional solidification of a novel third-generation nickel-based single crystal superalloy turbine blade. A combined experimental and multi-physics numerical simulation approach was adopted. The results indicate that [...] Read more.

This paper investigates the formation mechanism and key influencing factors of freckle defects that arise during the directional solidification of a novel third-generation nickel-based single crystal superalloy turbine blade. A combined experimental and multi-physics numerical simulation approach was adopted. The results indicate that freckle formation primarily originates from solutal convection, which subsequently triggers a cascade of processes, including the development of convection-induced segregation channels, flow-driven dendrite fragmentation, and the migration and aggregation of dendrite fragments. The severity of freckling is closely dependent on both the casting’s position within the furnace and its local geometric characteristics. Castings located in regions with poorer heating conditions exhibit lower temperature gradients and slower solidification rates, significantly increasing their susceptibility to freckle formation. Similarly, on a given casting, the side subjected to less favorable heating is more prone to freckle initiation. The freckle number varies non-monotonically along the blade height, increasing from 3 to a maximum of 16, with a temporary decrease near the platform and a final reduction near the top. This trend is mainly attributed to thickness-dependent channel segregation, as well as freckle propagation into the interior and coalescence at higher positions. This study provides a crucial theoretical basis for understanding the formation mechanism of freckle defects in nickel-based single crystal superalloys and offers valuable guidance for optimizing blade manufacturing processes, reducing solidification defects, and enhancing blade quality and service performance. Full article

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37 pages, 11045 KB

Open AccessEditor’s ChoiceReview

Lattice Thermal Transport in Polymers: Atomistic Insights, Modeling Advances, and Design Perspectives

by Haoran Cui, Theodore Maranets, Yan Wang, Yifei Jin and Lei Cao

Crystals 2026, 16(4), 242; https://doi.org/10.3390/cryst16040242 - 3 Apr 2026

Viewed by 1873

Abstract

Polymers are widely used in applications ranging from flexible electronics and thermal interface materials to structural composites and textile fabrics. Their inherently low

κ

, strongly governed by molecular structure and morphology, makes polymers a challenging yet scientifically rich class of materials for [...] Read more.

Polymers are widely used in applications ranging from flexible electronics and thermal interface materials to structural composites and textile fabrics. Their inherently low

κ

, strongly governed by molecular structure and morphology, makes polymers a challenging yet scientifically rich class of materials for thermal transport studies. Over the past two decades, modeling and simulation have played a central role in elucidating heat transport mechanisms in polymers and in guiding the rational design of polymer systems with enhanced or tunable thermal properties. This review provides a comprehensive overview of the theoretical frameworks and computational approaches used to model thermal transport in polymers. We discuss atomistic methods including density functional theory, molecular dynamics, and first-principles Boltzmann transport equation approaches, as well as emerging data-driven and machine learning-based techniques. Special attention is devoted to the effects of chain conformation, crystallinity, orientation, interchain coupling, interfaces, and nanocomposite architectures. Current challenges and future research directions are highlighted, with particular emphasis on multiscale modeling, method integration, and predictive materials design. Full article

(This article belongs to the Section Organic Crystalline Materials)

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17 pages, 3210 KB

Open AccessEditor’s ChoiceArticle

Supersaturation-Pathway-Controlled Gypsum Crystallization and Morphology: Nucleation- vs. Growth-Dominated Regimes with a Polycarboxylate Superplasticizer

by Faiz M. Kakar, Parichehr Pourattar, Christian Pritzel, Torsten Kowald and Manuela S. Killian

Crystals 2026, 16(4), 241; https://doi.org/10.3390/cryst16040241 - 3 Apr 2026

Cited by 1 | Viewed by 1279

Abstract

Gypsum (CaSO₄·2H₂O) crystallization is highly sensitive to the supersaturation pathway, which governs the balance between nucleation and crystal growth and ultimately controls growth morphology. In this study, gypsum was synthesized via two contrasting routes—diffusion-controlled crystallization and rapid precipitation—using identical [...] Read more.

Gypsum (CaSO₄·2H₂O) crystallization is highly sensitive to the supersaturation pathway, which governs the balance between nucleation and crystal growth and ultimately controls growth morphology. In this study, gypsum was synthesized via two contrasting routes—diffusion-controlled crystallization and rapid precipitation—using identical reactant systems to enable a direct comparison of distinct kinetic regimes. A polycarboxylate-based superplasticizer was incorporated to investigate pathway-dependent additive effects. Time-resolved observations reveal that rapid precipitation is characterized by high nucleation density under steep supersaturation, whereas diffusion-controlled crystallization proceeds under gradually increasing supersaturation with restricted nucleation and sustained anisotropic growth. Powder X-ray diffraction confirms the formation of phase-pure gypsum under all conditions. Scanning electron microscopy shows that the presence of the superplasticizer reduces crystal number density and modifies crystal habit in both pathways, although the extent and manifestation of these effects depend strongly on the governing kinetic regime. Under diffusion-controlled conditions, the increasing superplasticizer dosage promotes the transition from elongated to more tabular morphologies, while rapid precipitation results in dense, intergrown aggregates under high supersaturation. Overall, the results demonstrate that the effectiveness of the superplasticizer is not intrinsic but depends on the crystallization pathway. These findings provide new insight into how supersaturation profiles mediate the interplay between additive interactions and growth processes, enabling improved control over gypsum crystal morphology. Full article

(This article belongs to the Special Issue Advanced Research on Microstructure Evolution in Crystalline Materials)

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15 pages, 8086 KB

Open AccessEditor’s ChoiceArticle

Exploring the Interplay Between Soaked Time, Exposed Area, and Solution Volume on Mineral Loss in Enamel and Dentin

by Boyu Ning, Xuefei Chen, Go Inoue, Ling Yu, Heba Elsubeihi, Morihiro Takamatsu, Lin Fan and Yasushi Shimada

Crystals 2026, 16(4), 238; https://doi.org/10.3390/cryst16040238 - 2 Apr 2026

Viewed by 860

Abstract

Soaking bovine tooth blocks in demineralization solution is a widely used method to simulate caries-like demineralization for further experimental studies. The objective of this study was to evaluate the degree and depth of mineral loss in bovine enamel and dentin blocks under various [...] Read more.

Soaking bovine tooth blocks in demineralization solution is a widely used method to simulate caries-like demineralization for further experimental studies. The objective of this study was to evaluate the degree and depth of mineral loss in bovine enamel and dentin blocks under various controlled conditions and to investigate the relationships between these factors and mineral loss, providing guidance for researchers to achieve targeted demineralization outcomes. A total of 54 enamel blocks and 54 dentin blocks were divided into 18 groups according to the exposed area and solution volume and then immersed in demineralization solution. Micro-CT scans were performed before immersion, as well as after 1, 2, 3, 7, and 10 days of immersion. The results were analyzed using data analysis software and subsequently summarized into graphical representations. The analysis revealed that soaking time and solution volume showed positive correlations with mineral loss, whereas the exposed area was negatively correlated with mineral loss. Mean mineral loss increased significantly with immersion time in all groups (e.g., from 6314 to 25,670 vol%·μm in the dentin 3 × 3 mm², 50 mL group, p < 0.05). After 7 days, specimens immersed in larger solution volumes showed significantly greater mineral loss than those immersed in smaller volumes (p < 0.05). In addition, larger exposed areas resulted in greater mineral loss after 3 days of immersion. Mean mineral loss followed a power function relationship with time when the solution volume was sufficiently high relative to the exposed surface area. In contrast, when the solution volume was limited, a logarithmic relationship between time and mineral loss was observed. Given its superior stability, the mean mineral loss appears to be a more reliable indicator for assessing tooth demineralization. Based on our results, more controlled and reproducible demineralization conditions can be achieved, which may contribute to improving the reliability of in vitro caries models and facilitating the evaluation of preventive and therapeutic strategies. Full article

(This article belongs to the Special Issue Novel Dental Materials for Caries Prevention)

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11 pages, 840 KB

Open AccessEditor’s ChoiceArticle

The Crystal Structure of the GG-Rich DNA Quadruplex Sequence GGGGTTTTGGGG in Presence of Zn²⁺ and K⁺ Ions

by Hristina Sbirkova-Dimitrova, Hristo Gerginov and Boris L. Shivachev

Crystals 2026, 16(4), 223; https://doi.org/10.3390/cryst16040223 - 27 Mar 2026

Viewed by 1114

Abstract

The structural characterization of GG-rich DNA sequences in presence of metal ions provides essential insight into quadruplex stability and ion-dependent conformational specifics. We report the crystal structure of the GG-quadruplex formed by the sequence GGGGTTTTGGGG in the presence of Zn²⁺, K [...] Read more.

The structural characterization of GG-rich DNA sequences in presence of metal ions provides essential insight into quadruplex stability and ion-dependent conformational specifics. We report the crystal structure of the GG-quadruplex formed by the sequence GGGGTTTTGGGG in the presence of Zn²⁺, K⁺, and Na⁺. It was deposited in the RCSB Protein Data Bank under the accession code 9FTA. The structure was determined by single-crystal X-ray diffraction at a resolution of 2.49 Å in the space group P2₁2₁2₁. It reveals a parallel-stranded, two-G-tetrad stabilized by K⁺ ions within the central channel, while Na⁺ and Zn²⁺ occupy peripheral and groove-associated sites. Zn²⁺ ions are engaged in noncanonical coordination interactions with phosphate oxygens and structured water molecules, contributing to lattice stabilization and subtle adjustments in groove dimensions. The T4 loop forms a compact, ordered motif that contributes to crystal packing rather than intramolecular G4 stabilization. The presence of mixed cations produces a sole lattice architecture mediated by ions that provides structural insight into how bivalent and monovalent metals mutually modulate G-quadruplex topology. These results suggest a basis for understanding the specific ion effects on G4 structures and may direct the design of metal open DNA architectures. Full article

(This article belongs to the Special Issue Structural Studies in Drug Discovery and Development: From the Lead to the Pharmaceutical Form, 2nd Edition)

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15 pages, 3873 KB

Open AccessEditor’s ChoiceArticle

Novel Method to Prepare Perovskite MAPb_0.75Sn_0.25I₃ Solar Cells with Sn²⁺/Sn⁴⁺ Oxidation Mitigation via Molarity Reduction in a Non-Inert Atmosphere Processing

by José E. Erro-Quiñonez, Ricardo Rangel-Segura, Ricardo Rodríguez Carvajal, Frank Romo-García, Oscar E. Contreras-López, Carlos F. Arias-Ramos, Francisco Enrique Cancino-Gordillo and Rafael García-Gutiérrez

Crystals 2026, 16(4), 222; https://doi.org/10.3390/cryst16040222 - 26 Mar 2026

Viewed by 1220

Abstract

Sn-based perovskites offer lower lead content but face a major challenge: Sn²⁺ oxidizes readily, which has led most research groups to use gloveboxes and chemical additives during processing. Here, we investigate whether precursor molarity alone can mitigate this oxidation problem in ambient [...] Read more.

Sn-based perovskites offer lower lead content but face a major challenge: Sn²⁺ oxidizes readily, which has led most research groups to use gloveboxes and chemical additives during processing. Here, we investigate whether precursor molarity alone can mitigate this oxidation problem in ambient air. MAPb_0.75Sn_0.25I₃ solar cells with mesoporous N–i–P architecture were prepared from 1.0 M and 0.9 M solutions by spin-coating with ethyl acetate antisolvent, under standard lab conditions (28–34 °C, 30–45% RH). The characterization included SEM, XRD, XPS, profilometry, and J–V measurements. The 0.9 M concentration produced thinner films (275 nm vs. 474 nm), better Sn²⁺/Sn⁴⁺ ratios (16.5%/83.5% vs. 77.6%/22.4% by XPS), lower band gaps (1.51–1.52 vs. 1.55–1.56 eV), and larger grains. Device efficiency increased from 1.61 ± 0.68% (1.0 M) to 4.53 ± 0.91% (0.9 M), with the best cell reaching 5.91%—about 85% of our MAPbI₃ control (6.96%). After one month of storage, 0.9 M cells retained 61% efficiency compared to 37% for 1.0 M devices. These findings demonstrate that a simple reduction in precursor molarity can substantially suppress Sn⁴⁺ formation during ambient fabrication, providing a practical route for laboratories without controlled atmospheres. Full article

(This article belongs to the Special Issue Advances in Optoelectronic Materials)

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14 pages, 2339 KB

Open AccessEditor’s ChoiceArticle

Crystal Structures of a Thermophilic Cutinase from Chaetomium thermophilum Reveal Conformational Dynamics of the Catalytic Lid Loop

by Ryohei Nojima, Lirong Chen, Minami Kurokawa, Sho Ito and Tatsuya Nishino

Crystals 2026, 16(4), 217; https://doi.org/10.3390/cryst16040217 - 24 Mar 2026

Viewed by 1147

Abstract

Microbial cutinases are promising biocatalysts for polymer recycling. Here, we investigated the structural basis of catalytic activation in a thermophilic cutinase from Chaetomium thermophilum (CtCut). Differential scanning calorimetry revealed a three-state thermal unfolding pathway (Tm = 66.4 °C and 69.5 °C), [...] Read more.

Microbial cutinases are promising biocatalysts for polymer recycling. Here, we investigated the structural basis of catalytic activation in a thermophilic cutinase from Chaetomium thermophilum (CtCut). Differential scanning calorimetry revealed a three-state thermal unfolding pathway (Tm = 66.4 °C and 69.5 °C), indicating hierarchical stability. To capture distinct conformational states while avoiding affinity-tag artifacts, we employed both tag-free and tagged constructs. We determined apo-structures of wild-type and S136A mutant CtCut at 1.7 Å resolution and a complementary inhibitor complex at 2.65 Å. In the apo-state, a chloride ion coordinated the electrostatically pre-organized active site, while the catalytic H204 adopted a solvent-exposed, inactive loop conformation. In the inhibitor complex, p-nitrophenol displaced the chloride, establishing a characteristic oxyanion hole network. Concomitantly, the “lid” loop transitioned to an open state, with H204 exhibiting pronounced conformational heterogeneity across eight independent molecules. These complementary structures provide structural evidence for conformational dynamics of the catalytic lid loop, consistent with the conformational cycling model previously proposed for a mesophilic homolog. Full article

(This article belongs to the Special Issue Crystallography of Enzymes (2nd Edition))

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14 pages, 4006 KB

Open AccessEditor’s ChoiceArticle

Controlled Growth of Large-Area Graphite Single Crystals at Atmospheric Pressure and High Temperature from a Metal Flux

by Thomas Poirier, Dylan Evans, Ishika Thakur, Morgen L. Smith, Placidus B. Amama, Gaihua Ye, Rui He and James H. Edgar

Crystals 2026, 16(3), 207; https://doi.org/10.3390/cryst16030207 - 18 Mar 2026

Viewed by 764

Abstract

In this study, the growth of high-quality graphite single crystals from a molten metal flux at atmospheric pressure was optimized. The crystals were precipitated from a saturated iron–carbon solution by slowly cooling (4 °C/h) from a maximum temperature to reduce the carbon solubility. [...] Read more.

In this study, the growth of high-quality graphite single crystals from a molten metal flux at atmospheric pressure was optimized. The crystals were precipitated from a saturated iron–carbon solution by slowly cooling (4 °C/h) from a maximum temperature to reduce the carbon solubility. The graphite flakes were >25 square millimeters in area and >10 microns thick, with individual crystal grains as large as 1.2 mm². The crystals were (0002) oriented, as determined by X-ray diffraction. The high structural quality of the graphite crystals was verified by Raman spectroscopy. For graphite with the natural distribution of carbon isotopes, the G-peak at 1580 cm⁻¹ was narrow (~12 cm⁻¹) and the defect peak (D-peak) was absent. To demonstrate the process versatility, graphite crystals enriched in the ¹³C isotope were grown at 5 degrees of enrichment. The Raman G-peak linearly shifted from 1580 cm⁻¹ to 1520 cm⁻¹ for graphite crystals enriched from 1 to 99% ¹³C. The etch pit densities from defect-sensitive etching ranged from 0 to 1.6 × 10⁸ per cm². The process was refined by examining the grain size and quality as functions of the carbon concentration in the starting sources, the carrier gas composition, and maximum temperature. The simplicity of this process suggests it can be scaled to produce very large graphite crystals that would be suitable for a wide range of technologies. Full article

(This article belongs to the Section Crystal Engineering)

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14 pages, 2938 KB

Open AccessEditor’s ChoiceArticle

Effect of Crystal-to-Detector Distance Variations on Serial Femtosecond Crystallography Data Collected at PAL-XFEL

by Ki Hyun Nam, Sehan Park and Jaehyun Park

Crystals 2026, 16(3), 203; https://doi.org/10.3390/cryst16030203 - 17 Mar 2026

Cited by 1 | Viewed by 844

Abstract

Serial femtosecond crystallography (SFX) using X-ray free electron lasers (XFELs) enables the determination of room-temperature structures of biological macromolecules without radiation damage. The accuracy of detector geometry parameters, including the crystal-to-detector distance (CTDD), is critical for reliable data processing. In SFX experiments, the [...] Read more.

Serial femtosecond crystallography (SFX) using X-ray free electron lasers (XFELs) enables the determination of room-temperature structures of biological macromolecules without radiation damage. The accuracy of detector geometry parameters, including the crystal-to-detector distance (CTDD), is critical for reliable data processing. In SFX experiments, the CTDD may shift during data collection due to changes in the experimental setup or installation of the sample delivery system. Such CTDD variations can affect the quality of SFX datasets; however, their impact has not been fully elucidated in the context of SFX data processing. In this study, we investigated the influence of CTDD variations on SFX datasets collected at Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) with thermolysin, lysozyme, and glucose isomerase crystals processed by four indexing algorithms. At the optimized CTDD, the distribution of unit cell parameters exhibited a Gaussian pattern; however, it became distorted as the CTDD deviated further from the optimal value. Data analysis indicated that the CTDD tolerance for successful data processing and structure determination was approximately ±3–5 mm from the optimized CTDD. These findings provide insight into indexing behavior in SFX data processing at PAL-XFEL and offer practical guidance for improving data processing efficiency. Full article

(This article belongs to the Section Biomolecular Crystals)

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20 pages, 2694 KB

Open AccessEditor’s ChoiceArticle

Formability of AA7021-T4 Sheet Alloy Under Changing Strain Path Conditions: Experiments and Crystal Plasticity Modeling

by Md. Zahidul Sarkar, Joshua Lim, Sarah Sanderson, David T. Fullwood, Marko Knecevic and Michael P. Miles

Crystals 2026, 16(3), 199; https://doi.org/10.3390/cryst16030199 - 15 Mar 2026

Viewed by 601

Abstract

The formability of AA7021-T4 sheets under changing strain paths was investigated via a novel crystal plasticity model and associated experimentation. The motivation was to advance simulation tools for process design of limited-ductility 7xxx alloys, with important applications in the automotive industry. Pre-strains were [...] Read more.

The formability of AA7021-T4 sheets under changing strain paths was investigated via a novel crystal plasticity model and associated experimentation. The motivation was to advance simulation tools for process design of limited-ductility 7xxx alloys, with important applications in the automotive industry. Pre-strains were applied in biaxial and plane-strain tension using Marciniak tooling, followed by uniaxial tensile testing to failure. Strain measurements were obtained by digital image correlation, while dislocation structures were characterized using high-resolution EBSD. A strain-gradient elasto-plastic self-consistent (SG-EPSC) model incorporating dislocation density-based hardening and backstress from geometrically necessary dislocations (GNDs) was employed to predict the stress–strain response and dislocation evolution. Results showed that pre-strains normalized by forming limit diagram (FLD) criteria produced comparable residual uniaxial tensile ductility, regardless of whether biaxial or plane-strain tension was applied, despite differences in absolute pre-strain levels. Both experiments and simulations revealed that GND density correlated with remaining ductility better than simple strain magnitude values. These findings indicate that AA7021-T4 retains greater formability under multiaxial strain path changes than expected from FLD-based considerations. The combined experimental–modeling approach demonstrates the value of incorporating microstructure-based variables, such as GNDs, into forming assessments of high-strength aluminum alloys, with implications for their potential use in automotive lightweighting development. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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11 pages, 2677 KB

Open AccessEditor’s ChoiceArticle

Large-Size Barium Nitrate Crystal Growth and Large-Energy, High-Efficiency Raman Frequency Conversion to Yellow–Orange Waveband

by Xiaojing Lin, Hongkai Ren, Pingzhang Yu, Guowei Liu, Zhengping Wang, Xun Sun and Xinguang Xu

Crystals 2026, 16(3), 198; https://doi.org/10.3390/cryst16030198 - 13 Mar 2026

Viewed by 688

Abstract

Stimulated Raman scattering (SRS) with Raman crystals is widely recognized as an effective technical approach for achieving high-efficiency lasers at specific wavelengths. However, due to crystal size limitations, it is challenging to generate large-energy Raman lasers while simultaneously considering the laser damage threshold [...] Read more.

Stimulated Raman scattering (SRS) with Raman crystals is widely recognized as an effective technical approach for achieving high-efficiency lasers at specific wavelengths. However, due to crystal size limitations, it is challenging to generate large-energy Raman lasers while simultaneously considering the laser damage threshold of optical components. To overcome this limitation, in this paper we describe the successful fabrication of a large-aperture barium nitrate Raman gain medium using the directional template growth technique. Employing this large-aperture Raman medium and a 532 nm pulse laser as the excitation source, a large-energy, high-efficiency yellow–orange waveband laser system was constructed. When injected with 886.7 mJ pump energy at 532 nm, the Raman laser achieved a maximum output energy of 556.2 mJ, corresponding to an optical-to-optical conversion efficiency of 62.7%. This represents a significant advancement in single-pulse energy for barium nitrate Raman lasers. Large-energy yellow–orange wavelength lasers have applications in the clinical treatment of skin diseases and microfluidic chip manufacturing. Full article

(This article belongs to the Section Crystal Engineering)

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15 pages, 2046 KB

Open AccessEditor’s ChoiceArticle

Structure Analysis and Luminescence Properties of Octaethyl(pyrene-tetrakis(biphenyl))tetrakis(phosphonate)

by Aysenur Limon, Marcus N. A. Fetzer and Christoph Janiak

Crystals 2026, 16(3), 196; https://doi.org/10.3390/cryst16030196 - 13 Mar 2026

Cited by 1 | Viewed by 821

Abstract

We present a modular building block strategy for synthesizing phosphonated polyaromatic systems as an alternative to the conventional late-stage phosphonation of prefabricated aromatic scaffolds, which often requires harsh conditions and has limited tolerance for functional groups. A monophosphonated biphenyl building block was obtained [...] Read more.

We present a modular building block strategy for synthesizing phosphonated polyaromatic systems as an alternative to the conventional late-stage phosphonation of prefabricated aromatic scaffolds, which often requires harsh conditions and has limited tolerance for functional groups. A monophosphonated biphenyl building block was obtained via nickel-catalyzed phosphonation of dibromobiphenyl at 170 °C for three hours. This synthesis is more economical and milder than typical high-temperature palladium systems. In parallel, a borated pyrene derivative was prepared by Suzuki–Miyaura borylation. The final palladium-catalyzed Suzuki cross-coupling reaction produced the target compound, octaethyl(pyrene-tetrakis(biphenyl))tetrakis(phosphonate), Et₈-PyTPPE. Single-crystal X-ray diffraction reveals a centrosymmetric molecule that crystallizes in the triclinic space group P–1, with the inversion center located at the central C–C bond of the pyrene core. The pyrene unit is essentially planar, while the biphenylphosphonate arms are highly twisted relative to the core and to each other. The crystal packing is dominated by weak intermolecular interactions, and no significant π–π stacking is observed. Hirshfeld surface analysis shows that H···H (60.5%) and C···H (22.5%) contacts predominate, while O···H interactions (14.4%) with phosphoryl oxygen atoms represent the most relevant directed contacts. From photophysical investigations, Et₈-PyTPPE exhibits blue fluorescence (λ_em. = 452 nm) in solution and aggregation-induced red-shifted emission with nanosecond lifetimes in the solid state, confirming purely fluorescent behavior. Full article

(This article belongs to the Special Issue Synthesis, Crystal Structures and Hirshfeld Surface Analysis of Coordination Compounds (3rd Edition))

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10 pages, 1959 KB

Open AccessEditor’s ChoiceArticle

In Situ Synchrotron Radiation Computed Tomography Study on Fatigue Damage Evolution of Additively Manufactured Ti-6Al-4V Alloy

by Hui Wang, Guangcheng Fan and Yu Xiao

Crystals 2026, 16(3), 195; https://doi.org/10.3390/cryst16030195 - 11 Mar 2026

Viewed by 1096

Abstract

Additive manufacturing (AM) of Ti-6Al-4V alloy is widely used in aerospace and medical fields due to its excellent strength and corrosion resistance. However, the microstructural heterogeneity induced by the AM process often results in fatigue properties inferior to those of their forged counterparts. [...] Read more.

Additive manufacturing (AM) of Ti-6Al-4V alloy is widely used in aerospace and medical fields due to its excellent strength and corrosion resistance. However, the microstructural heterogeneity induced by the AM process often results in fatigue properties inferior to those of their forged counterparts. Synchrotron Radiation Computed Tomography (SR-CT) was employed to conduct an in situ three-dimensional investigation of fatigue damage evolution in Ti-6Al-4V alloy fabricated via laser powder bed fusion (LPBF). Experimental results revealed phenomena of crack bridging and deflection, accompanied by the consistent presence of local high-density zones (LHDZs) throughout the fatigue damage progression. Combined with quantitative analysis of crack propagation rates, the influence of LHDZs on fatigue damage evolution was analyzed, and the relationship between AM processes, LHDZs, and fatigue damage was discussed. The results indicate that the basket-weave α-phase microstructure in Ti-6Al-4V prepared by LPBF exhibits a high correlation with the distribution of LHDZs, and the orientation of LHDZs aligns with the crack propagation direction. By adjusting process parameters such as cooling rate and temperature gradient, the formation of LHDZs can be modified, thereby influencing the fatigue properties of the material. This provides theoretical support for achieving process optimization of the fatigue properties of Ti-6Al-4V alloy prepared via LPBF. Full article

(This article belongs to the Special Issue Applications of Additive Manufacturing and Numerical Simulation in High-Performance Metallic Materials)

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11 pages, 1936 KB

Open AccessEditor’s ChoiceArticle

Effect of Lapping Parameters on Material Removal Rate and Surface Roughness of GaN (0001) Plane

by Hao Zhou, Yongliang Shao, Baoguo Zhang, Haixiao Hu, Yongzhong Wu and Xiaopeng Hao

Crystals 2026, 16(3), 190; https://doi.org/10.3390/cryst16030190 - 11 Mar 2026

Viewed by 782

Abstract

As a critical pretreatment process for chemical and mechanical polishing (CMP), the lapping roughness of gallium nitride (GaN) crystals directly influences the outcome of subsequent polishing and the reliability of final devices. This study systematically investigates the key factors affecting the lapping performance [...] Read more.

As a critical pretreatment process for chemical and mechanical polishing (CMP), the lapping roughness of gallium nitride (GaN) crystals directly influences the outcome of subsequent polishing and the reliability of final devices. This study systematically investigates the key factors affecting the lapping performance of GaN single crystals, focusing on abrasive type, particle size, and spindle speed, and elucidates their mechanisms in regulating material removal rate (MRR) and surface roughness. Using a micro-thickness gauge and controlled variable method, the material removal depth of the (0001) plane of GaN was accurately measured. The results show that the MRR increases with the increase in abrasive particle size within a certain range, albeit at the cost of increased surface roughness. Meanwhile, the spindle speed and MRR exhibit a positive correlation under specific conditions. Considering these lapping parameters, a balance between high MRR and controlled roughness can be achieved, providing a technical foundation for efficient and precise lapping of GaN crystals and facilitating the fabrication of GaN-based devices. Full article

(This article belongs to the Special Issue Advances in the Growth and Application of Nitride Crystals)

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20 pages, 8212 KB

Open AccessEditor’s ChoiceArticle

Study on the Static Recrystallization Behavior of Ti-2Al-2.5Zr Alloy Tubes

by Wenzhen Fan, Jun Wu, Qi Xu and Xuefei Huang

Crystals 2026, 16(3), 187; https://doi.org/10.3390/cryst16030187 - 10 Mar 2026

Cited by 1 | Viewed by 744

Abstract

This study systematically investigated the static recrystallization behavior and microstructural evolution of cold-rolled Ti-2Al-2.5Zr alloy tubes subjected to isothermal annealing at 650–800 °C. Electron backscatter diffraction (EBSD), optical microscopy, and microhardness testing were used to analyze recrystallization kinetics, grain size, grain boundary character, [...] Read more.

This study systematically investigated the static recrystallization behavior and microstructural evolution of cold-rolled Ti-2Al-2.5Zr alloy tubes subjected to isothermal annealing at 650–800 °C. Electron backscatter diffraction (EBSD), optical microscopy, and microhardness testing were used to analyze recrystallization kinetics, grain size, grain boundary character, texture evolution, and strain energy release under different annealing temperatures and times. The results show that with increasing annealing temperature, the recrystallization incubation time is significantly shortened and the recrystallization rate increases nonlinearly; the times required for full recrystallization at 650, 700, 750, and 800 °C are 480 min, 25 min, 20 min, and 15 min, respectively. Compared with the other annealing temperatures, annealing at 700 °C yields finer, more uniform equiaxed grains and lower texture intensity, while at higher temperatures, recrystallization and recovery proceed too rapidly, which is unfavorable for fine control of the microstructure. After completion of recrystallization, the alloy microhardness stabilizes at approximately 200 HV. Based on the Avrami kinetics model, the recrystallization activation energy of the Ti-2Al-2.5Zr alloy tubes was calculated to be approximately 303.9 kJ/mol, providing a theoretical basis for optimizing the annealing process. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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24 pages, 7190 KB

Open AccessEditor’s ChoiceArticle

Effects of Loading Direction on Mechanical Behavior of Core–Shell Cu-Al Nanoparticles Under Uniform Compressive Loading-Molecular Dynamics Study

by Phillip Tomich, Michael Zawadzki and Iman Salehinia

Crystals 2026, 16(3), 186; https://doi.org/10.3390/cryst16030186 - 10 Mar 2026

Viewed by 881

Abstract

The mechanical behavior of metallic core–shell nanoparticles is critical for their use as reinforcement particles and additive manufacturing feedstocks, yet their deformation mechanisms remain incompletely understood. This study employs molecular dynamics simulations to investigate the compressive response of a Cu-core/Al-shell nanoparticle and compares [...] Read more.

The mechanical behavior of metallic core–shell nanoparticles is critical for their use as reinforcement particles and additive manufacturing feedstocks, yet their deformation mechanisms remain incompletely understood. This study employs molecular dynamics simulations to investigate the compressive response of a Cu-core/Al-shell nanoparticle and compares it with solid Cu, solid Al, and a hollow Al shell of the same size under uniaxial loading along ⟨100⟩, ⟨110⟩, ⟨111⟩, and ⟨112⟩ directions. The single-material nanoparticles show strong anisotropy: solid Cu exhibits orientation-dependent transitions from dislocation slip to deformation twinning, while introducing a void to form a hollow Al shell reduces stiffness and strength, confines plasticity to the shell wall, and suppresses extended load-bearing twins. The Cu–Al core–shell nanoparticle combines these behaviors in an orientation-dependent manner. Under ⟨110⟩ and ⟨112⟩ loading, deformation is largely shell-dominated, whereas ⟨100⟩ and ⟨111⟩ loading more strongly activates the Cu core. Mechanistically, ⟨100⟩ is characterized by Shockley partial activity and junction/lock formation in the Al shell coupled with twinning in the Cu core; ⟨110⟩ shows primarily shell partials with limited core involvement; ⟨111⟩ promotes partial-dislocation activity in both shell and core; and ⟨112⟩ produces localized, twin-dominated bands in the Al shell with shell-thickness-dependent twin extension into the Cu core. These trends are rationalized using Schmid factor considerations for

\{111\} ⟨ 110 ⟩

slip and

\{111\} ⟨ 112 ⟩

partial/twinning shear, together with the effects of faceted free surfaces and the Cu–Al interface. The core–shell geometry enables two concurrent interface-mediated pathways, i.e., (i) stress transfer and reduced cross-interface transmission and (ii) circumferential bypass within the shell, which together yield only slight flow-stress increases over solid Al while markedly reducing stress serrations compared with both solid Cu and solid Al. Across all orientations, the core–shell structures also exhibit delayed yielding (higher yield strain) relative to solid Cu, indicating enhanced ductility. The results provide an atomistic basis for designing Cu–Al core–shell nanoparticles for robust particle-based processing and additive manufacturing feedstock, and for informing multiscale models with mechanism-resolved, orientation-dependent inputs. Full article

(This article belongs to the Special Issue Structure, Properties, and Applications of Nanomaterials and Thin Films)

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16 pages, 713 KB

Open AccessEditor’s ChoiceArticle

Geometric Resonance Analysis of Superconductivity in CaC₆: Hexagonal and Rhombohedral Descriptions in the Roeser–Huber Framework

by Michael R. Koblischka and Anjela Koblischka-Veneva

Crystals 2026, 16(3), 184; https://doi.org/10.3390/cryst16030184 - 9 Mar 2026

Viewed by 660

Abstract

The superconducting transition temperature of

{CaC}_{6}

is investigated within the Roeser–Huber (RH) formalism using both rhombohedral and hexagonal crystallographic representations. While these two descriptions are crystallographically equivalent, they differ in their geometric construction of superconducting paths and near-atom environments. In the rhombohedral [...] Read more.

The superconducting transition temperature of

{CaC}_{6}

is investigated within the Roeser–Huber (RH) formalism using both rhombohedral and hexagonal crystallographic representations. While these two descriptions are crystallographically equivalent, they differ in their geometric construction of superconducting paths and near-atom environments. In the rhombohedral representation, only translationally closed Ca–Ca vectors consistent with the primitive lattice are considered, yielding three symmetry-distinct RH paths. In the hexagonal representation, the same superconducting channels are expressed in an expanded conventional cell, where some paths appear as unfolded or symmetry-related sublattice connections. For each representation, the RH path lengths and effective near-atom counts are evaluated and used to compute the superconducting transition temperature. The rhombohedral description yields

T_{c}^{(calc)} = 10.4

K, while the hexagonal representation gives

T_{c}^{(calc)} = 10.9

K, both in good agreement with the experimental value

T_{c}^{(\exp)} = 11.5

K. The difference between the calculated values amounts to approximately 5%. These results show that the underlying RH superconducting channels and their near-atom environments are representation independent, while minor quantitative differences in

T_{c}^{(calc)}

arise from metric redistribution of equivalent paths. This directly confirms that the RH formalism captures intrinsic structural features of superconductivity rather than artifacts of unit-cell representation. Full article

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14 pages, 1606 KB

Open AccessEditor’s ChoiceArticle

Influence of Chirality and Anions on the Structure of Dipyridyl Ag(I) Complexes and Coordination Polymers

by Diksha U. Sawant and David R. Turner

Crystals 2026, 16(3), 181; https://doi.org/10.3390/cryst16030181 - 9 Mar 2026

Cited by 1 | Viewed by 565

Abstract

Chiral and racemic forms of a pyridyl ligand (R-L and rac-L, respectively), containing urea groups at their core and synthesised by the condensation of 3-aminopyridine and α-methylbenzylisocyante, were incorporated into silver complexes. The resulting species depend on [...] Read more.

Chiral and racemic forms of a pyridyl ligand (R-L and rac-L, respectively), containing urea groups at their core and synthesised by the condensation of 3-aminopyridine and α-methylbenzylisocyante, were incorporated into silver complexes. The resulting species depend on the enantiopurity of the ligand alongside an influence from the counter-anion. The enantiopure ligand generated isomorphous, one-dimensional polymeric compounds [Ag(R-L)X] (where X = NO₃, CF₃SO₃) or [Ag(R-L)]X (where X = BF₄, PF₆). The polymeric chains, connected by N and O coordination of the ligands, have outwards facing urea groups that form hydrogen bonds to the counter-anions, which play little role in determining the overall structure. Despite all syntheses containing an excess of Ag(I) salt, the racemic ligand formed only discrete complexes of [Ag(rac-L)₂]⁺ in the presence of each of the above anions. Three of these complexes contain ligands of the same chirality (i.e., complexes with R,R and S,S ligand pairs within the centrosymmetric structures) with only the PF₆-containing compound being different. The anions play a role in dictating the structure of hydrogen-bonded chains, although PF₆⁻ is unique with urea···urea interactions present between complexes. Overall, this system highlights the nuances associated with predicting the structure, and even speciation, of related chiral/achiral systems in addition to influences of counter-anions on structural motifs. Full article

(This article belongs to the Special Issue Synthesis, Crystal Structures and Hirshfeld Surface Analysis of Coordination Compounds (3rd Edition))

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27 pages, 7899 KB

Open AccessEditor’s ChoiceArticle

Microfluidic Fabrication of TiO₂–Hydrogel Photocatalytic Composites for Water Treatment

by Sergio J. Peñas-Núñez, Diego Lecumberri, Adrián Durán and Francisco J. Peñas

Crystals 2026, 16(3), 175; https://doi.org/10.3390/cryst16030175 - 5 Mar 2026

Cited by 1 | Viewed by 1008

Abstract

Water purification and treatment methods are becoming increasingly complex due to the use of new additives, solvents, pesticides, dyes, and other emerging pollutants in industry, agriculture, and households. Consequently, the search for new water treatment techniques and materials that can help reduce this [...] Read more.

Water purification and treatment methods are becoming increasingly complex due to the use of new additives, solvents, pesticides, dyes, and other emerging pollutants in industry, agriculture, and households. Consequently, the search for new water treatment techniques and materials that can help reduce this environmental impact has become a major focus in the field of green chemistry. In this work, the photocatalytic degradation capacity of composites containing TiO₂ nanoparticles (TNPs) for the removal of organic pollutants in water was studied. The TNPs were immobilized in bio-based hydrogel microparticles, which were prepared using microfluidic techniques. The composition of the dispersed phase was optimized with a lab-on-a-chip device, resulting in composite microparticles with a narrow size distribution. UV–visible spectroscopy results indicated that increasing the concentration of TNPs in the hydrogel microparticles enhanced the photodegradation performance of the new composite. Remarkably, it was able to efficiently degrade nearly 90% of reference dyes after four adsorption–desorption cycles. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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15 pages, 1274 KB

Open AccessEditor’s ChoiceArticle

Halogen Bonding vs. π-Stacked (Charge-Transfer) Interaction of Phenothiazine

by Sarah Glunt, Md Mahiuddin Sarker, Kiran Avinash, Matthias Zeller and Sergiy V. Rosokha

Crystals 2026, 16(3), 177; https://doi.org/10.3390/cryst16030177 - 5 Mar 2026

Cited by 2 | Viewed by 1174

Abstract

Phenothiazine is a heteroaromatic molecule capable of various noncovalent interactions, including halogen bonding and π-stacked association. Despite its broad use in functional materials and pharmaceutical ingredients, a systematic comparison of these interaction modes has been lacking. Here, we report a combined experimental and [...] Read more.

Phenothiazine is a heteroaromatic molecule capable of various noncovalent interactions, including halogen bonding and π-stacked association. Despite its broad use in functional materials and pharmaceutical ingredients, a systematic comparison of these interaction modes has been lacking. Here, we report a combined experimental and computational study of intermolecular interactions of phenothiazine with a prototypical halogen-bond (HaB) donor (tetrabromomethane), planar π-electron acceptors (tetracyanopyrazine and tetrafluoro-p-benzoquinone), and multifunctional species capable of both interaction types (iodo- and bromo-3,5-dinitrobenzenes). X-ray structural analysis revealed that CBr₄ forms exclusively C–Br···π halogen bonds with the aromatic rings of phenothiazine, whereas all π-acceptors yield alternating donor–acceptor stacks characterized by multiple short contacts indicative of multicenter interactions. Notably, co-crystals of iodo- and bromodinitrobenzenes with phenothiazine display only π-stacked architectures. Density-functional calculations showed that isolated HaB complexes involving N, S, or π sites of phenothiazine possess comparable binding energies (≈−3 kcal mol⁻¹), whereas π-stacked complexes are substantially stronger (≈−9–12 kcal mol⁻¹). QTAIM, NCI, NBO, and energy-decomposition analyses indicated that while amounts of charge transfer in halogen-bonded and π-stacked complexes are comparable, the enhanced stability of the latter originates primarily from a large dispersion contribution. These results rationalize the solid-state preference for π-stacking over halogen bonding in systems where both motifs are accessible and clarify the hierarchy and physical origin of noncovalent interactions involving phenothiazine, providing guidance for the design of supramolecular assemblies and functional materials based on this versatile electron donor. Full article

(This article belongs to the Section Crystal Engineering)

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15 pages, 4013 KB

Open AccessEditor’s ChoiceArticle

In Situ Synthesized Manganese Ferrite/Carbon Composite Nano-Material: A Novel Electrode Material for High-Performance Supercapacitors

by Tshiamo Baloyi, Ndeye Fatou Diop, Rashed Ali Mohamed Adam, Erence Nkuna, Gift Rutavi, Motlalepula Rebecca Mhlongo, Ncholu Manyala and Vusani Muswa Maphiri

Crystals 2026, 16(3), 171; https://doi.org/10.3390/cryst16030171 - 2 Mar 2026

Viewed by 718

Abstract

This study presents an in situ synthesis of a novel manganese ferrite/carbon (MF/C) composite material via a citrate sol–gel route followed by calcination in an inert argon (Ar) atmosphere. The structural and morphological and porosity properties were characterized using X-ray diffraction (XRD), Fourier [...] Read more.

This study presents an in situ synthesis of a novel manganese ferrite/carbon (MF/C) composite material via a citrate sol–gel route followed by calcination in an inert argon (Ar) atmosphere. The structural and morphological and porosity properties were characterized using X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), and N₂ gas physisorption analysis. Electrochemical evaluation of the MF/C in a 3 M KOH electrolyte in a three-electrode configuration showed a high specific capacity of 39.26 mAh g⁻¹ at 1 Ag⁻¹ and a rate capability of 69% at 5 Ag⁻¹ and an equivalent series resistance (ESR) of 0.798 Ω. Subsequently, an asymmetric hybrid supercapacitor device (MF/C//AC) was fabricated using MF/C as the positive electrode and human-derived activated carbon (AC) as the negative electrode. The assembled device exhibited remarkable performance, with a wide operating voltage window of 1.4 V, a high sweeping potential of 1 V s⁻¹, a specific capacity, energy, power and maximum power of 42.4 mAhg⁻¹, 16.35 Wh kg⁻¹, 1944 W kg⁻¹ and 236 kW kg⁻¹, respectively, and excellent capacitance retention of 92% after 15,000 charge–discharge cycles. The in situ preparation approach significantly reduced synthesis time and cost compared to conventional multi-step methods, as less equipment was required, while still achieving comparable or superior electrochemical performance to other supercapacitors in the literature. Full article

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10 pages, 1646 KB

Open AccessEditor’s ChoiceArticle

Surface Energies and Interface Structures of CuZr₂ Crystals

by Hong-Wen Han, Xi-Fang Chen and Jian-Gang Yao

Crystals 2026, 16(3), 169; https://doi.org/10.3390/cryst16030169 - 28 Feb 2026

Viewed by 428

Abstract

Cu-Cr-Zr alloy is a typical precipitation-strengthened alloy, and the interface stability between precipitates and the Cu matrix significantly influences the alloy’s strength and properties. However, research in this field is currently lacking. In light of this, we focus on the CuZr₂ precipitate [...] Read more.

Cu-Cr-Zr alloy is a typical precipitation-strengthened alloy, and the interface stability between precipitates and the Cu matrix significantly influences the alloy’s strength and properties. However, research in this field is currently lacking. In light of this, we focus on the CuZr₂ precipitate and investigate its surface and interface properties using the GGA/PBE method within density functional theory. The results indicate that the (100) and (010) surfaces of CuZr₂ share the same atomic structure, with both being stoichiometric surfaces. By fitting the relationship between the total energy of surface supercells with varying numbers of atoms and the number of atomic layers, the surface energy values were accurately calculated. The (100) surface is a non-stoichiometric surface, featuring three surface terminations: Cu, Zr1, and Zr2, with the Zr2 termination being the most stable. Finally, based on experimental observations, the atomic structure of the CuZr₂ (010)/Cu (110) interface was predicted. The calculated interfacial energy reveals that the lattice mismatch between the CuZr₂ precipitate and the Cu matrix significantly affects interfacial stability. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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9 pages, 1465 KB

Open AccessEditor’s ChoiceArticle

Optimizing Sintering Temperature for Enhanced Piezoelectric Performance in PMT-PNT-PZT Ceramics

by Shaoyang Yuan, Junjun Wang, Junjun He, Liqiang Liu, Yufang Jiao, Yan Mu and Fengmin Wu

Crystals 2026, 16(3), 163; https://doi.org/10.3390/cryst16030163 - 27 Feb 2026

Viewed by 1226

Abstract

The 0.006Pb(Mn_1/3Ta_2/3)O₃-0.114Pb(Ni_1/3Ta_2/3)O₃-0.43PbZrO₃-0.45PbTiO₃ lead-based ceramics (PMT-PNT-PZT) were synthesized via the solid-state reaction at different sintering temperatures to study their effects on phase structure, microstructure, and electrical properties. The maximum [...] Read more.

The 0.006Pb(Mn_1/3Ta_2/3)O₃-0.114Pb(Ni_1/3Ta_2/3)O₃-0.43PbZrO₃-0.45PbTiO₃ lead-based ceramics (PMT-PNT-PZT) were synthesized via the solid-state reaction at different sintering temperatures to study their effects on phase structure, microstructure, and electrical properties. The maximum mechanical quality factor (Q_m) and relative permittivity (ε_r) were achieved at the sintering temperature of 1200 °C. The piezoelectric constant d₃₃ of 400 pC/N was obtained at 1180 °C, which is attributed to the high grain density and the significant contribution from the remanent polarization and permittivity product (P_rε_r = 39,115 μC/cm²). Compared with commercial PZT4 ceramics, the present composition sintered at 1180 °C exhibits an optimal balance between d₃₃ and Q_m, together with the superior figure of merit (FOM = 2.04 × 10⁵ pC/N). Furthermore, it demonstrates excellent temperature stability in electromechanical coupling performance. Full article

(This article belongs to the Special Issue Recent Research on Piezoelectric Ceramics)

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19 pages, 6832 KB

Open AccessEditor’s ChoiceArticle

Effects of Al and O Concentrations on the Practical Properties of TiAl4822 for Jet Engine Blades and the Feasibility of Machining Chip Reuse

by Toshimitsu Tetsui and Kazuhiro Mizuta

Crystals 2026, 16(3), 156; https://doi.org/10.3390/cryst16030156 - 24 Feb 2026

Viewed by 475

Abstract

Maintaining a consistent quality of TiAl4822 blades used in jet engines is crucial, even when compositional variations occur during production. This study investigates the optimal Al and O concentration ranges that yield favorable practical properties. Additionally, the feasibility of reusing machining chips as [...] Read more.

Maintaining a consistent quality of TiAl4822 blades used in jet engines is crucial, even when compositional variations occur during production. This study investigates the optimal Al and O concentration ranges that yield favorable practical properties. Additionally, the feasibility of reusing machining chips as a low-cost melting feedstock is explored. The results indicate that both impact resistance at 25 °C and machinability remain unaffected or even improve at O concentrations up to at least 0.13 wt%. Moreover, materials containing 0.13 wt% O exhibit the widest optimal range of Al concentrations (46.8–47.4 at%), but was narrower at lower or higher Al concentrations. The influence of the α₂-phase ratio on impact resistance is substantially greater than that of O concentration, with the optimal range being 0.2–0.3. Furthermore, a new pre-treatment method is developed to reuse machining chips containing large amounts of water-soluble cutting oil. This method involves removing C through atmospheric heating after ultrasonic cleaning using acetone. Furthermore, TiAl4822 castings including these preprocessed chips exhibit superior properties compared with those of chip-free low-O materials, despite the higher O concentration. These findings demonstrate that moderate O enrichment is tolerable, and even beneficial, enabling cost-effective recycling in TiAl4822 blade production. Full article

(This article belongs to the Special Issue Advances in High-Performance Alloys)

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24 pages, 6102 KB

Open AccessEditor’s ChoiceArticle

Nucleation Studies of Lactobacillus brevis Alcohol Dehydrogenases in a Stirred Crystallizer Monitored by In Situ Multi-Angle Dynamic Light Scattering (MADLS)

by Julian Mentges, Daniel Bischoff and Dirk Weuster-Botz

Crystals 2026, 16(2), 148; https://doi.org/10.3390/cryst16020148 - 19 Feb 2026

Viewed by 854

Abstract

Nucleation remains one of the least understood steps during protein crystallization, although it strongly impacts product quality attributes, including total crystal numbers, final crystal size distributions, and thus downstream processing. In this work, the nucleation behavior of Lactobacillus brevis alcohol dehydrogenase (Lb [...] Read more.

Nucleation remains one of the least understood steps during protein crystallization, although it strongly impacts product quality attributes, including total crystal numbers, final crystal size distributions, and thus downstream processing. In this work, the nucleation behavior of Lactobacillus brevis alcohol dehydrogenase (LbADH) wild type (WT) and five mutants (Q207D, Q126H, K32A, D54F, and T102E) is investigated in a stirred 7 mL crystallizer monitored by in situ multi-angle dynamic light scattering (MADLS). Nucleation was studied with highly pure homotetrameric LbADHs by establishing a crystallization, lyophilization, and re-solubilization protocol combined with size exclusion chromatography (SEC) and size exclusion high-performance liquid chromatography (SE-HPLC), yielding tetramer purities above 94% and removing low molecular weight impurities. During stirred batch crystallizations initiated by the addition of polyethyleneglycol 550 monomethyl ether (PEG 550 MME), SEC and SE-HPLC revealed decreasing tetramer peak areas but essentially constant peak apex positions, indicating that no long-lasting oligomeric intermediates accumulate at detectable levels. Time-resolved MADLS measurements using a custom-made flow-through cuvette in a bypass to the stirred crystallizer uncovered transient cluster populations. All protein variants exhibited an initial tetramer peak, followed by the formation of larger aggregates and a rapid rise in signal above a hydrodynamic diameter of 1000 nm, coinciding with the onset of macroscopic turbidity. A simple mesoscale nucleation model was formulated, yielding end-of-nucleation times, crystallized fractions, critical soluble concentrations, and apparent nucleation rate constants. The crystal contact mutations modulate both the timing and magnitude of the nucleation burst (rapid build-up of nuclei/cluster populations). The mutant Q207D showed strongly attenuated nucleation compared to the WT, whereas the other mutants (K32A, D54F, and particularly T102E) display markedly accelerated nucleation at nearly invariant critical concentrations. The combined workflow demonstrates how in situ MADLS, together with a tailored kinetic description, can provide mechanistic insight into protein nucleation in stirred batch crystallizers. Full article

(This article belongs to the Section Biomolecular Crystals)

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12 pages, 2331 KB

Open AccessEditor’s ChoiceArticle

Structural and Proton Conduction Modifications in RbH₂PO₄ Crystals upon Heating Under Different Environments

by Cristian E. Botez and Alex D. Price

Crystals 2026, 16(2), 147; https://doi.org/10.3390/cryst16020147 - 17 Feb 2026

Cited by 1 | Viewed by 892

Abstract

We used synchrotron X-ray diffraction (XRD) and ac-impedance spectroscopy (AIS) to uncover the structural and chemical modifications undergone by RbH₂PO₄ (RDP) at intermediate temperatures (150 °C < T < 300 °C) and investigate their relationship with RDP’s proton conductivity, σ. [...] Read more.

We used synchrotron X-ray diffraction (XRD) and ac-impedance spectroscopy (AIS) to uncover the structural and chemical modifications undergone by RbH₂PO₄ (RDP) at intermediate temperatures (150 °C < T < 300 °C) and investigate their relationship with RDP’s proton conductivity, σ. Nyquist plots collected on RDP samples sealed in a small volume (~50 mL) of dry air show a gradual increase in σ upon heating from 180 to 260 °C, but not the three-order-of-magnitude superprotonic jump observed in the Cs-based compound CsH₂PO₄ (CDP) within the same temperature range. Correspondingly, XRD measurements using synchrotron radiation (λ = 0.922 Å) on RDP crystalline powders sealed in a quartz capillary exhibit no evidence of a monoclinic-to-cubic superprotonic phase transition like the one observed in CDP. Instead, these temperature-resolved powder XRD patterns demonstrate that the intermediate-temperature RDP monoclinic phase (P2₁/m, a = 7.733 Å, b = 6.189 Å, c = 4.793 Å, and β = 109.21 deg) persists up to the melting point of the title compound. Our most significant finding comes from heating RDP under high pressure (P = 1 GPa), which leads to markedly different structural behavior. Indeed, our full profile refinements against XRD data collected on RDP crystals compressed at ~1 GPa show evidence of a polymorphic phase transition (at T_c = 300 °C) to a high-temperature cubic phase (Pm-3m, a = 4.784 Å) that is isomorphic with its CDP counterpart. This is significant, as it indicates that the superprotonic conduction in phosphate solid acids is not cation-specific, and a general highly efficient proton conduction mechanism is present in the high-temperature phases of these materials. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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13 pages, 7141 KB

Open AccessEditor’s ChoiceArticle

The Influence of Coating Thickness and Interface Microcracks on Contact Stresses in Ceramic Bearings: A Discrete Element Study

by Ying Li, Xiaojiao Gu, Jinghua Li, Xiaozheng Xu and He Lu

Crystals 2026, 16(2), 146; https://doi.org/10.3390/cryst16020146 - 16 Feb 2026

Viewed by 653

Abstract

This paper investigates the contact stress induced by a rigid sphere sliding on a coating-ceramic system. A discrete element model incorporating a ceramic substrate, a surface coating, and a rigid sphere is developed. The influences of the coating grain elastic modulus, coating surface [...] Read more.

This paper investigates the contact stress induced by a rigid sphere sliding on a coating-ceramic system. A discrete element model incorporating a ceramic substrate, a surface coating, and a rigid sphere is developed. The influences of the coating grain elastic modulus, coating surface friction coefficient, coating thickness, and interface microcrack defects on the stress distribution within the system are analyzed. The results indicate that a higher coating-to-substrate elastic modulus ratio increases the overall stress but reduces the interfacial shear stress. A lower surface friction coefficient is more beneficial for hard coatings. The relatively optimal coating thickness (h/a) is approximately 0.5. When interface microcrack defects are present, stress concentrations occur at their locations. Longer interface microcracks lead to greater stress concentration, and the interfacial concentrated stress increases with crack length. Full article

(This article belongs to the Section Polycrystalline Ceramics)

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19 pages, 1714 KB

Open AccessEditor’s ChoiceArticle

Effects of Uniaxial Distortion on the Stability of Square Skyrmion Crystals in Noncentrosymmetric Magnets

by Satoru Hayami

Crystals 2026, 16(2), 139; https://doi.org/10.3390/cryst16020139 - 14 Feb 2026

Viewed by 791

Abstract

We theoretically investigate the influence of uniaxial distortion on the stability of square skyrmion crystals, which are described as double-Q spin textures composed of two orthogonal spiral modulations, in noncentrosymmetric magnets. An effective spin model incorporating momentum-resolved frustrated exchange interactions and Dzyaloshinskii–Moriya [...] Read more.

We theoretically investigate the influence of uniaxial distortion on the stability of square skyrmion crystals, which are described as double-Q spin textures composed of two orthogonal spiral modulations, in noncentrosymmetric magnets. An effective spin model incorporating momentum-resolved frustrated exchange interactions and Dzyaloshinskii–Moriya (DM) interactions is analyzed using simulated-annealing calculations at low temperatures. The results reveal that uniaxial distortion drives a transformation from the double-Q square skyrmion crystal to a single-Q tilted conical spiral or vertical spiral state. The low-temperature phase diagrams further show that the stability region of the skyrmion crystal expands with increasing the magnitude of the DM interaction, making the phase more robust against the uniaxial anisotropy between exchange interactions parallel and perpendicular to the distortion axis. This study provides insight into how uniaxial strain and DM interactions cooperatively influence the formation and stability of skyrmion crystal phases in noncentrosymmetric magnetic systems. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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17 pages, 2964 KB

Open AccessEditor’s ChoiceArticle

Synthesis, Structure, and Properties of the Complex Zintl Phase Eu₉Zn_4.5As₉: A Candidate Topological Insulator and Thermoelectric Material

by Spencer R. Watts, Olha Pokhvata, Thimira Kandabadage, Bhushan Thipe, Xiaojian Bai, Svilen Bobev and Sviatoslav Baranets

Crystals 2026, 16(2), 137; https://doi.org/10.3390/cryst16020137 - 13 Feb 2026

Cited by 2 | Viewed by 1372

Abstract

Reported are the synthesis and detailed analysis of the crystal and electronic structure of the novel Zintl phase Eu₉Zn_4.5As₉. This material was identified in the densely populated Eu–Zn–As compositional space. For structure determination and for property measurements, [...] Read more.

Reported are the synthesis and detailed analysis of the crystal and electronic structure of the novel Zintl phase Eu₉Zn_4.5As₉. This material was identified in the densely populated Eu–Zn–As compositional space. For structure determination and for property measurements, suitable single crystals of this compound were grown from either Sn- or Pb-flux. Single-crystal X-ray diffraction methods indicate that Eu₉Zn_4.5As₉ crystallizes in the orthorhombic crystal system with the space group Pnma (a = 12.1953(7) Å, b = 4.3730(2) Å, c = 42.674(2) Å) and is formally isostructural to Ca₉Mn_4+xSb₉, the less common “9–4–9” type. The structure is heavily disordered, with multiple partially occupied sites, yet, according to the Zintl-Klemm formalism, a charge-balanced composition (Eu²⁺)₉(Zn²⁺)_4.5(As³⁻)₉ is attained. Electronic structure calculations for a model, disorder-free structure indicate no energy gap between the valence and the conduction bands and suggest (semi)metallic behavior. Preliminary susceptibility measurements confirm the expected divalent nature of Eu²⁺ ([Xe] 4f⁷ ground state). Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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33 pages, 3782 KB

Open AccessEditor’s ChoiceReview

Photocatalytic Reduction of CO₂ by Bi-Based Semiconductor: A Review on Recent Progress

by Yuming Lu, Jingkai Yan, Wei He, He Guo, Feng Liu, Zhenghua Yang and Wenxin Hu

Crystals 2026, 16(2), 128; https://doi.org/10.3390/cryst16020128 - 9 Feb 2026

Viewed by 1686

Abstract

Photocatalytic reduction of CO₂ into valuable solar fuels represents a promising strategy to address both energy crises and carbon emissions. Bismuth-based semiconductors have emerged as attractive visible-light-driven photocatalysts due to their suitable band structures, layered architectures, and tunable morphologies. This review systematically [...] Read more.

Photocatalytic reduction of CO₂ into valuable solar fuels represents a promising strategy to address both energy crises and carbon emissions. Bismuth-based semiconductors have emerged as attractive visible-light-driven photocatalysts due to their suitable band structures, layered architectures, and tunable morphologies. This review systematically summarizes recent advances in Bi-based photocatalysts for CO₂ photoreduction. First, the fundamental principles and key challenges of CO₂ photoreduction are outlined. Subsequently, the structural and electronic characteristics of typical Bi-based materials, including Bi₂O₃, Bi₂S₃, Bi₂MO₆ (M = W; Mo), BiVO₄, and BiOX (X = Cl; Br; I), are discussed. Emphasis is placed on design strategies to enhance photocatalytic performance, such as vacancy engineering, microstructure control, crystal facet engineering, heterojunction construction, cocatalyst loading, and their combinations. A comprehensive comparison of catalytic activities under various conditions is also provided. Finally, current limitations and future perspectives are highlighted, aiming to guide the rational design of efficient and stable Bi-based photocatalysts for CO₂ conversion. Full article

(This article belongs to the Special Issue Advances in Photocatalytic Technology and Materials)

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18 pages, 11347 KB

Open AccessEditor’s ChoiceArticle

Kinetics of Oxidation at High Temperature and Degradation States of Cr-Free Al-Containing Cobalt and Nickel Alloys Reinforced by TaC Carbides

by Patrice Berthod

Crystals 2026, 16(2), 125; https://doi.org/10.3390/cryst16020125 - 8 Feb 2026

Viewed by 757

Abstract

Two cobalt alloys and one nickel alloy, containing Ta and C in similar atomic contents and either 5 or 10 wt.% Al, were cast. Their microstructures and their oxidation behaviors in air at 1200 °C over 50 h were investigated. All contained eutectic [...] Read more.

Two cobalt alloys and one nickel alloy, containing Ta and C in similar atomic contents and either 5 or 10 wt.% Al, were cast. Their microstructures and their oxidation behaviors in air at 1200 °C over 50 h were investigated. All contained eutectic script-like TaC carbides and a dendritic matrix which was either single-phased (FCC) or double-phased (FCC + Co₃Al). The cobalt sample with 5 wt.% oxidized catastrophically, became thinner, lost all its TaC, and was covered by a thick oxide shell (outer CoO and inner mixture of CoO, CoAl₂O₄ and Ta-rich oxides). The two other alloys, Ni-based with 5 wt.% Al and Co-based with 10 wt.% Al, oxidized more slowly, with a mass gain kinetic slightly lower than that for chromia-forming alloys at 1200 °C and a continuous duplex oxide scale made of an outer MAl₂O₄ spinel and inner Al₂O₃ scales. This evidences the existence of two Al content thresholds, depending on the base element, that must be exceeded to obtain acceptable oxidation behavior. Full article

(This article belongs to the Special Issue Microstructure Characterization and Design of Advanced Alloys)

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28 pages, 10791 KB

Open AccessEditor’s ChoiceArticle

CVD Monolayer MoS₂ Memtransistors for Chaotic Time-Series Prediction via Reservoir Computing

by Vladislav Kurtash, Lina Jaurigue and Jörg Pezoldt

Crystals 2026, 16(2), 116; https://doi.org/10.3390/cryst16020116 - 5 Feb 2026

Cited by 1 | Viewed by 772

Abstract

Monolayer

{MoS}_{2}

memtransistors offer gate-tunable hysteresis for neuromorphic reservoir computing, yet the role of operating window and fading-memory dynamics in CVD devices remains underexplored. We grow CVD monolayer

{MoS}_{2}

, fabricate back-gated memtransistors, and use a single device as a time-multiplexed [...] Read more.

Monolayer

{MoS}_{2}

memtransistors offer gate-tunable hysteresis for neuromorphic reservoir computing, yet the role of operating window and fading-memory dynamics in CVD devices remains underexplored. We grow CVD monolayer

{MoS}_{2}

, fabricate back-gated memtransistors, and use a single device as a time-multiplexed reservoir node for one-step Lorenz-63 prediction. Mobility, ON/OFF, hysteresis, and drift are quantified to identify stable, tunable bias regimes. We used a transistor with field-effect mobility on the order of

10 {cm}^{2} V^{- 1} s^{- 1}

, an ON/OFF ratio above

10^{5}

, and a moderate hysteresis window quantified by

H \approx 2.1 μ

A·V at

V_{DS} = 50

mV and

H \approx 17 μ

A·V at

V_{DS} = 500

mV over

V_{GS} \in [- 10, 30]

V. Performance is bias/memory-limited rather than FET-metric-limited. Sweeping gate-window and reservoir hyperparameters shows an optimum at intermediate hysteresis with moderate drift. Performance improves when the input clock matches the fading-memory time, achieving normalized root mean square error (NRMSE) = 0.09 for one-step Lorenz-63 x-prediction. Device-level statistics (discussed in the main text) show that, despite substantial scattering in electrical parameters, the resulting device-to-device NRMSE variation remains very small under fixed operating conditions. Classical FET metrics are not limiting here; NRMSE improvement instead requires engineering the hysteresis spectrum and gate stack. The demonstration of Lorenz-63 prediction using CVD-grown monolayer

{MoS}_{2}

memtransistors highlights their potential as a wafer-scalable platform for compact chaotic time-series predictions. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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18 pages, 1815 KB

Open AccessEditor’s ChoiceArticle

Influence of Isopropanol on Kinetics of Hydrogen Evolution Reaction Examined at Nickel Foam Electrodes in Alkaline Solution

by Wiktoria Abramczyk, Bogusław Pierożyński, Tomasz Mikołajczyk and Kazimierz Warmiński

Crystals 2026, 16(2), 114; https://doi.org/10.3390/cryst16020114 - 5 Feb 2026

Cited by 1 | Viewed by 1058

Abstract

The current work examines the impact of isopropanol (IPA) on the electrochemical characteristics of nickel foam and Pd-modified Ni foam electrodes in a 0.1 M NaOH medium, with respect to the kinetics of the hydrogen evolution reaction (HER) over the temperature range of [...] Read more.

The current work examines the impact of isopropanol (IPA) on the electrochemical characteristics of nickel foam and Pd-modified Ni foam electrodes in a 0.1 M NaOH medium, with respect to the kinetics of the hydrogen evolution reaction (HER) over the temperature range of 20–40 °C. Comparative HER/IPA examinations are presented for a highly catalytic polycrystalline Pt electrode. Electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and cathodic Tafel polarization experiments were carried out in this work, where the IPA concentrations ranged from 1.0 × 10⁻⁵ to 1.0 × 10⁻³ M. The introduction of small amounts of isopropyl alcohol into the working electrolyte noticeably facilitated the catalytic efficiency of the hydrogen evolution reaction on the surface of Ni foam electrodes. This is most likely related to the fact that IPA molecules undergo partial electrooxidation to acetone (qualitatively confirmed by GC-MS analysis) during initial CV cycling, which is believed to significantly diminish the surface tension phenomenon during the HER, thus promoting hydrogen bubble separation from the electrode surface. It should also be noted that acetone will continuously be produced at the Pt anode, making it essential to consider further migration of (CH₃)₂CO molecules to the working cell compartment. Most importantly, isopropanol was found not to undergo significant surface electrosorption on the nickel foam-based catalysts, which could otherwise significantly inhibit the hydrogen evolution reaction On the contrary, the presence of IPA in the electrolyte solution seems to have a detrimental effect on the kinetics of both the HER and the UPDH (underpotential deposition of H) processes on the surface of the polycrystalline Pt electrode, which is a superior electrochemical catalyst for HER, but highly susceptible to surface contamination. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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15 pages, 7847 KB

Open AccessEditor’s ChoiceArticle

Microstructures of Fe-16wt%S-2wt%Si in Partial and Complete Melt Regions at High Pressures: Implications for Dynamics in Small Planetary Cores

by Erin Lenhart, Wenjun Yong and Richard A. Secco

Crystals 2026, 16(2), 113; https://doi.org/10.3390/cryst16020113 - 5 Feb 2026

Viewed by 856

Abstract

Regions of partial melt of Fe-S-Si alloys at high pressures may arise during planetary formation or at the boundary of the inner and outer cores of small terrestrial planetary bodies. Melting experiments were performed on Fe-16wt%S-2wt%Si samples in a multi-anvil apparatus across the [...] Read more.

Regions of partial melt of Fe-S-Si alloys at high pressures may arise during planetary formation or at the boundary of the inner and outer cores of small terrestrial planetary bodies. Melting experiments were performed on Fe-16wt%S-2wt%Si samples in a multi-anvil apparatus across the range 2–13 GPa with quench temperatures in partial and complete melt regions. A phase diagram is constructed from electron microprobe analyses, back-scattered electron imaging, and electrical resistivity measurements. Microstructures arising in post-quench samples include Turing patterns of Fe and FeS in the partial melt, dendritic Fe structures with tertiary arms in the partial and complete melt, and Fe-S-Si miscible regions in the complete melt. These melt structures may arise broadly or locally in small Fe-S planetary cores with consequences for the energetics of the core. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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12 pages, 2019 KB

Open AccessEditor’s ChoiceArticle

Negative Photoconductivity in Ultranarrow-Gap Semiconductors

by Catherine Masie, Alexander Frenkel, Gela Kipshidze, Dmitri Donetski and Gregory Belenky

Crystals 2026, 16(2), 117; https://doi.org/10.3390/cryst16020117 - 5 Feb 2026

Cited by 1 | Viewed by 1057

Abstract

A decrease in conductivity under illumination, known as negative photoconductivity, has been observed in various semiconductors and is commonly attributed to trapping of excess carriers by deep centers. Here, we demonstrate that negative photoconductivity can instead arise from a rapid increase in carrier [...] Read more.

A decrease in conductivity under illumination, known as negative photoconductivity, has been observed in various semiconductors and is commonly attributed to trapping of excess carriers by deep centers. Here, we demonstrate that negative photoconductivity can instead arise from a rapid increase in carrier scattering in ultranarrow-gap semiconductors with degenerate carrier statistics. This behavior is explained by the combined effects of enhanced optical phonon emission scattering and an increase in effective mass due to band filling. Experimentally, photoconductivity was measured over wide ranges of excitation and temperature in unintentionally doped n-type short-period InAsSb_0.6/InAsSb_0.3 strained-layer superlattices (SLS), relevant for long-wavelength infrared optoelectronic devices. The resistive device impedance, weakly dependent on excess carrier concentration, simplifies broadband impedance matching to low-voltage CMOS driver electronics. At 77 K, 10.6 µm laser excitation led to an initial rise in conductivity, with a decrease observed above 10 W/cm². Full article

(This article belongs to the Special Issue The Cutting Edge of Energy Materials Research Aimed at Practical Application)

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17 pages, 6852 KB

Open AccessEditor’s ChoiceArticle

Liquid Crystal Dimers Based on Seven-Membered Bridged Stilbene Exhibiting Twist-Bend Nematic Phases

by Yoshimichi Shimomura, Bi Sheng, Yuki Arakawa, Riki Iwai and Gen-ichi Konishi

Crystals 2026, 16(2), 111; https://doi.org/10.3390/cryst16020111 - 3 Feb 2026

Cited by 3 | Viewed by 1841

Abstract

We report the first examples of bent-shaped LC dimers based on a seven-membered bridged stilbene. We synthesized nonylene- and ether-linked cyano-terminated dimers (sC9-tCN and sOC7O-tCN, respectively) and a homologous series of nonylene-linked alkyl-terminated dimers ( [...] Read more.

We report the first examples of bent-shaped LC dimers based on a seven-membered bridged stilbene. We synthesized nonylene- and ether-linked cyano-terminated dimers (sC9-tCN and sOC7O-tCN, respectively) and a homologous series of nonylene-linked alkyl-terminated dimers (sC9-tCn) with alkyl carbon atoms n = 1–6. Polarizing optical microscopy, differential scanning calorimetry, and X-ray diffraction measurement were employed to investigate the phase-transition behavior and LC phase structures. sC9-tCN and sOC7O-tCN only exhibited a nematic (N) phase, whereas sC9-tCn (n = 1–5) formed both the N_TB and N phases. sC9-tC5 additionally formed an unidentified X phase from the N_TB phase and sC9-tC6 exhibited a smectic A phase from the N phase. The weak dispersion force and intermolecular affinity provided by the terminal alkyl chains are likely to be preferable to the large dipole–dipole interactions by the cyano termini for the N_TB phase formation of the present dimers. The isotropic points of sC9-tCn showed an odd–even oscillation with n, whereas the N–N_TB phase transition temperatures were comparable. Remarkably, the N_TB stripe textures of sC9-tCn appeared perpendicular to the rubbing direction, and the N–N_TB phase transitions exhibited their second-order nature. This study revealed the unique N_TB phase properties of the 7-membered bridged stilbene-based LC dimers. Full article

(This article belongs to the Collection Liquid Crystals and Their Applications)

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21 pages, 17608 KB

Open AccessEditor’s ChoiceArticle

The Influence of Key Process Parameters in CMT Arc Welding Repair of ZL114A Aluminum Alloy

by Faming Shen, Xin Ding, Tongge Shao, Zenghui Cai, Qihao Chen, Xiangyu Duan, Bolun Dong and Sanbao Lin

Crystals 2026, 16(2), 106; https://doi.org/10.3390/cryst16020106 - 31 Jan 2026

Viewed by 586

Abstract

This study employed cold metal transfer (CMT) welding technology to repair defects in ZL114A aluminum alloy, investigating the influence of key repair welding parameters (preheating temperature, overlap amount, wire feed speed, welding speed) and ultimately obtaining defect-free repaired joints with relatively high tensile [...] Read more.

This study employed cold metal transfer (CMT) welding technology to repair defects in ZL114A aluminum alloy, investigating the influence of key repair welding parameters (preheating temperature, overlap amount, wire feed speed, welding speed) and ultimately obtaining defect-free repaired joints with relatively high tensile strength. Using a single-layer, single-pass bead-on-plate method, the effects of wire feed speed and welding speed on the spreading behavior of ZL114A melt on the substrate surface were studied. Through a two-pass, single-layer welding method, the influence of inter-pass overlap amount on the morphology of overlap welds was investigated. The effects of preheating temperature on the morphology, microstructure, and mechanical properties of the repaired specimens were examined by repair welding experiments on spherical crown grooves. The results indicate that to achieve favorable spreading of ZL114A droplets on the base material surface, the welding speed should be greater than 5 mm/s, and the wire feed speed should be within 7–9 m/min. When the overlap amounts are 65%, 70%, 75%, and 80%, the overlap welds are relatively flat, and lack-of-fusion defects are less likely to occur between the two weld passes. As the preheating temperature increases, the porosity defect rate in the repair weld decreases significantly, and the average grain size in the repair zone shows an increasing trend. The average grain size at the center of the repair weld is larger than that in the fusion zone. When the preheating temperature is 350 °C, no obvious porosity defects are observed in the repair weld. The proportion of high-angle grain boundaries increases significantly, and the maximum Kernel Average Misorientation (KAM) value also increases. The room-temperature tensile strength and Vickers hardness of the repaired specimens are superior to those of the original base material, with the tensile strength increasing by approximately 6 MPa and the Vickers hardness increasing by approximately 4 HV. Full article

(This article belongs to the Section Crystalline Metals and Alloys)

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14 pages, 2500 KB

Open AccessEditor’s ChoiceArticle

Mesoporous Structure and N-Doped Carbon Coating Skeleton Boosting High-Performance Nickel Phosphide Nanosheet-Based Electrocatalysts for Highly Efficient Electrocatalytic Hydrogen Evolution

by Yixuan Tang, Xiaowei Niu, Zhengjun Guan, Chengxin Wang, Xinyu Ma, Haonan Wang and Hongyuan Pan

Crystals 2026, 16(2), 100; https://doi.org/10.3390/cryst16020100 - 30 Jan 2026

Cited by 2 | Viewed by 842

Abstract

Earth-abundant nickel phosphide electrocatalysts show great potential for the hydrogen evolution reaction (HER), yet their efficiency requires further enhancement for practical applications. Herein, a novel in situ strategy is developed to synthesize a high-performance electrocatalyst on nickel foam (NF), composed of N-doped carbon-coated [...] Read more.

Earth-abundant nickel phosphide electrocatalysts show great potential for the hydrogen evolution reaction (HER), yet their efficiency requires further enhancement for practical applications. Herein, a novel in situ strategy is developed to synthesize a high-performance electrocatalyst on nickel foam (NF), composed of N-doped carbon-coated Ni₅P₄–Ni₃P heterostructures. This is achieved through the phosphidation and subsequent carbon coating of hydrothermally grown Ni(OH)₂ nanosheets. The resulting catalyst exhibits excellent HER activity in acidic media, requiring a low overpotential of only 63 mV to achieve a current density of 10 mA cm⁻². The superior performance stems from the synergistic effects of multiple factors: the porous nanosheet architecture and multi-phase interfaces provide abundant active sites, while the conductive N-doped carbon network significantly enhances charge-transfer kinetics and catalyst stability. This work presents an effective approach for designing efficient non-precious metal HER electrocatalysts. Full article

(This article belongs to the Special Issue Polymeric Materials for Sustainable Catalysis and Energy Applications)

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15 pages, 2486 KB

Open AccessEditor’s ChoiceArticle

Structure and Thermophysical Properties of Phase Change Materials Used in a Lithium-Ion Coin Battery Thermal Management System

by Mioara Zagrai, Olivia-Ramona Bruj, Alexandru Turza, Teodora Radu and Vasile Rednic

Crystals 2026, 16(2), 93; https://doi.org/10.3390/cryst16020093 - 28 Jan 2026

Cited by 2 | Viewed by 1102

Abstract

Phase change materials (PCMs) have emerged as an innovative solution in thermal energy storage and thermal management systems (TMS) owing to their outstanding latent heat of fusion during the phase change process. This study is especially addressed to the battery TMS based on [...] Read more.

Phase change materials (PCMs) have emerged as an innovative solution in thermal energy storage and thermal management systems (TMS) owing to their outstanding latent heat of fusion during the phase change process. This study is especially addressed to the battery TMS based on Organic PCMs for fast charging/discharging applications of lithium-ion batteries (LIBs). These fast processes generate excessive heat during operation, degrade battery performance, decrease energy efficiency, and reduce the lifespan and safety of batteries. Organic PCMs exhibit desirable properties, including high latent heat capacity, good thermal characteristics, low cost, and ease of integration. The major challenge for the successful application of organic PCM comprises its low thermal conductivity, which impacts the heat storage and release rates. PCM-based Paraffin Wax (PW) has been designed by including expanded graphite (EG) as a high thermal conductivity additive in high latent heat of paraffin wax. Experiments focused on the effects of heating methods (microwaves/S-type EG composition and conventional electric oven/S′-type EG composition) of expandable graphite on the thermophysical properties of different PW/EG composites. The crystal and chemical structure of the study samples were analyzed by X-ray diffraction and Fourier-Transform Infrared spectroscopy. The battery module created with PW/EG composites were ample examined using charging/discharging experiments at five different C-rates. The effect of current rates on battery surface temperature is investigated in two cases: with PCM cooling and with air cooling. A 20.43% decrease in battery temperature is found at 5C rate with PCM cooling and a maximum reduction in battery charging time of 43.77%. Full article

(This article belongs to the Special Issue Exploring New Materials for the Transition to Sustainable Energy)

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23 pages, 3718 KB

Open AccessEditor’s ChoiceArticle

Microstructural Observations, Mechanical Hierarchy, and Tribological Performance in CrFeMoV-Al_x High-Entropy Alloys

by Anthoula Poulia, Maria-Nikoleta Zygogianni, Christina Mathiou, Emmanuel Georgatis, Stavros Kiape, Spyros Kamnis and Alexander E. Karantzalis

Crystals 2026, 16(2), 88; https://doi.org/10.3390/cryst16020088 - 27 Jan 2026

Viewed by 690

Abstract

This work investigates the synthesis, thermodynamic phase stability and microstructural, mechanical and tribological behavior of the CrFeMoV alloy system and its Al-modified derivatives, CrFeMoV-Al2 and CrFeMoV-Al6, which belong to the family of high- and medium-entropy alloys. The studied systems were produced via Vacuum [...] Read more.

This work investigates the synthesis, thermodynamic phase stability and microstructural, mechanical and tribological behavior of the CrFeMoV alloy system and its Al-modified derivatives, CrFeMoV-Al2 and CrFeMoV-Al6, which belong to the family of high- and medium-entropy alloys. The studied systems were produced via Vacuum Arc Melting (VAM), followed by a comprehensive characterization. Thermodynamic and geometric phase-formation models were employed to predict the formation of BCC/Β2 solid solutions and the potential emergence of σ-type intermetallic compounds. An ML model was also employed to further predict elemental interactions and phase evolution. These predictions were experimentally confirmed via X-ray diffraction analysis, which verified the presence of a BCC matrix in all compositions, the presence of σ-phase precipitates whose volume fraction systematically reduced with Al inclusion and the gradual increase in the B2 phase with the increase in the Al content. Scanning electron microscopy and EDX analyses uncovered noticeable dendritic segregation, with Mo and Fe enrichment in dendrite cores and in interdendritic regions, respectively. Cr, V, and Al were more uniformly distributed. Mechanical property data derived by micro hardness testing demonstrated a high hardness of 816 HV for the base alloy, ascribed to σ-phase strengthening, followed by a progressive reduction in this value to 802 HV and 756 HV in Al-containing alloys due to the attenuation of σ-phase formation and the gradual increase in the B2 phase. Dry sliding wear results unveiled a positive correlation between wear resistance and hardness, confirming the beneficial role of intermetallic strengthening. Finally, nanoindentation tests shed light on the nanoscale mechanical response, confirming the trends observed at the microscale. Overall, the combination of thermodynamic modeling and experimental analysis provide a robust framework for understanding phase stability, microstructural evolution, and mechanical performance in Al-alloyed CrFeMoV high-entropy systems, while highlighting the potential of controlled Al additions to tailor microstructure and properties. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behaviour of Structural Materials: 3rd Edition)

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15 pages, 3325 KB

Open AccessEditor’s ChoiceArticle

Structural Study of L-Arabinose Isomerase from Latilactobacillus sakei

by Suwon Yang, Jeonghwa Cheon and Jung-Min Choi

Crystals 2026, 16(2), 84; https://doi.org/10.3390/cryst16020084 - 25 Jan 2026

Viewed by 864

Abstract

D-Tagatose is a rare sugar of interest as a low-calorie sweetener, and enzymatic isomerization of D-galactose is a practical production route. L-arabinose isomerase (L-AI; EC 5.3.1.4) is a promising catalyst for the above process, but many characterized L-AIs perform best at alkaline pH [...] Read more.

D-Tagatose is a rare sugar of interest as a low-calorie sweetener, and enzymatic isomerization of D-galactose is a practical production route. L-arabinose isomerase (L-AI; EC 5.3.1.4) is a promising catalyst for the above process, but many characterized L-AIs perform best at alkaline pH and high temperature and often require substantial divalent metal supplementation (e.g., Mn²⁺/Co²⁺), which complicates food-grade processing. Lactic acid bacteria (LAB) are attractive sources of food-compatible enzymes, yet structural information for LAB-derived L-AIs has been limited. Here, we report the 2.6 Å X-ray crystal structure of L-AI from Latilactobacillus sakei 23K (LsAI) and define its oligomeric assembly. Although the asymmetric unit contains a single monomer, crystallographic symmetry reconstructs a D₃-symmetric homohexamer composed of two face-to-face trimers, consistent with a higher-order assembly in solution. Interface analysis shows predominantly polar interaction networks, and normalized B-factor mapping reveals localized flexibility near active-site-proximal regions. These findings provide a structural basis for understanding LAB-derived L-AIs and support structure-guided engineering toward food-grade, low-metal biocatalysts for rare-sugar production. Full article

(This article belongs to the Special Issue Structure and Characterization of Enzymes)

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16 pages, 25861 KB

Open AccessEditor’s ChoiceArticle

Research on the Influence of Different Aging Temperatures on the Microstructure and Properties of GH2787 Alloy

by Yan Wang, Guohua Xu, Shengkai Gong, Shusuo Li, Juan Deng, Tianyi Wang, Zhen Liu and Wenqi Guo

Crystals 2026, 16(2), 81; https://doi.org/10.3390/cryst16020081 - 23 Jan 2026

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Abstract

This study systematically investigates the microstructural evolution and mechanical properties of GH2787 superalloy following solution treatment at 1140 °C and subsequent aging within the temperature range of 770 °C to 920 °C. The results indicate that aging at 770 °C and 820 °C [...] Read more.

This study systematically investigates the microstructural evolution and mechanical properties of GH2787 superalloy following solution treatment at 1140 °C and subsequent aging within the temperature range of 770 °C to 920 °C. The results indicate that aging at 770 °C and 820 °C promotes the precipitation of a high density of finely dispersed γ′ precipitates with minimal interparticle spacing. In contrast, a significant coarsening of the γ′ particles, accompanied by a sparse distribution and a notable increase in interparticle spacing, was observed at the higher aging temperatures of 870 °C and 920 °C. Mechanical characterization reveals that the ultimate tensile strength (UTS) and yield strength (YS) experienced a moderate decrease as the aging temperature increased from 770 °C to 820 °C, followed by a pronounced drop at 870 °C and 920 °C. Conversely, the impact toughness exhibited a non-monotonic trend: it gradually decreased, reaching a minimum at 820 °C, before rapidly increasing with further rises in aging temperature. Quantitative analysis of the strengthening contributions demonstrates that solid-solution and precipitation strengthening are the dominant mechanisms. The marked decline in yield strength at elevated aging temperatures is primarily attributed to the diminished precipitation strengthening effect due to γ′ coarsening. Furthermore, the variation in impact toughness can be linked to the proportion and size of dimples observed on the fracture surfaces, indicating a transition in the fracture mechanism driven by microstructural evolution. Full article

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29 pages, 4522 KB

Open AccessEditor’s ChoiceArticle

Machine Learning-Driven Prediction of Microstructural Evolution and Mechanical Properties in Heat-Treated Steels Using Gradient Boosting

by Saurabh Tiwari, Khushbu Dash, Seongjun Heo, Nokeun Park and Nagireddy Gari Subba Reddy

Crystals 2026, 16(1), 61; https://doi.org/10.3390/cryst16010061 - 15 Jan 2026

Viewed by 2062

Abstract

Optimizing heat treatment processes requires an understanding of the complex relationships between compositions, processing parameters, microstructures, and properties. Traditional experimental approaches are costly and time-consuming, whereas machine learning methods suffer from critical data scarcity. In this study, gradient boosting models were developed to [...] Read more.

Optimizing heat treatment processes requires an understanding of the complex relationships between compositions, processing parameters, microstructures, and properties. Traditional experimental approaches are costly and time-consuming, whereas machine learning methods suffer from critical data scarcity. In this study, gradient boosting models were developed to predict microstructural phase fractions and mechanical properties using synthetic training data generated from an established metallurgical theory. A 400-sample dataset spanning eight AISI steel grades was created based on Koistinen–Marburger martensite kinetics, the Grossmann hardenability theory, and empirical property correlations from ASM handbooks. Following systematic hyperparameter optimization via 5-fold cross-validation, gradient boosting achieved R² = 0.955 for hardness (RMSE = 2.38 HRC), R² = 0.949 for tensile strength (RMSE = 87.6 MPa), and R² = 0.936 for yield strength, outperforming the Random Forest, Support Vector Regression, and Neural Networks by 7–13%. Feature importance analysis identified the tempering temperature (38.4%), carbon equivalent (15.4%), and carbon content (13.0%) as the dominant factors. Model predictions demonstrated physical consistency with the literature data (mean error of 1.8%) and satisfied the fundamental metallurgical relationships. This methodology provides a scalable and cost-effective approach for heat treatment optimization by reducing experimental requirements based on learning curve analysis while maintaining prediction accuracy within the measurement uncertainty. Full article

(This article belongs to the Special Issue Investigation of Microstructural and Properties of Steels and Alloys)

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23 pages, 1151 KB

Open AccessEditor’s ChoiceArticle

CNN–BiLSTM–Attention-Based Hybrid-Driven Modeling for Diameter Prediction of Czochralski Silicon Single Crystals

by Pengju Zhang, Hao Pan, Chen Chen, Yiming Jing and Ding Liu

Crystals 2026, 16(1), 57; https://doi.org/10.3390/cryst16010057 - 13 Jan 2026

Viewed by 752

Abstract

High-precision prediction of the crystal diameter during the growth of electronic-grade silicon single crystals is a critical step for the fabrication of high-quality single crystals. However, the process features high-temperature operation, strong nonlinearities, significant time-delay dynamics, and external disturbances, which limit the accuracy [...] Read more.

High-precision prediction of the crystal diameter during the growth of electronic-grade silicon single crystals is a critical step for the fabrication of high-quality single crystals. However, the process features high-temperature operation, strong nonlinearities, significant time-delay dynamics, and external disturbances, which limit the accuracy of conventional mechanism-based models. In this study, mechanism-based models denote physics-informed heat-transfer and geometric models that relate heater power and pulling rate to diameter evolution. To address this challenge, this paper proposes a hybrid deep learning model combining a convolutional neural network (CNN), a bidirectional long short-term memory network (BiLSTM), and self-attention to improve diameter prediction during the shoulder-formation and constant-diameter stages. The proposed model leverages the CNN to extract localized spatial features from multi-source sensor data, employs the BiLSTM to capture temporal dependencies inherent to the crystal growth process, and utilizes the self-attention mechanism to dynamically highlight critical feature information, thereby substantially enhancing the model’s capacity to represent complex industrial operating conditions. Experiments on operational production data collected from an industrial Czochralski (Cz) furnace, model TDR-180, demonstrate improved prediction accuracy and robustness over mechanism-based and single data-driven baselines, supporting practical process control and production optimization. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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