Crystals

14 pages, 5321 KB

Open AccessEditor’s ChoiceArticle

Facile Low-Temperature Deposition of Seedless Nanocrystalline Diamond Films from CH₄/Ar Gas Mixtures

by Luis Medina-Zazueta, Frank Romo-García, Miguel Martínez-Gil, Rolando Flores-Ochoa, Mathías Martinez-Gil, Dainet Berman-Mendoza, Antonio Ramos-Carrazco, Gerardo Valenzuela-Hernández, Ch. J. Salas-Juárez, Carlos A. Pérez-Rábago and Rafael García-Gutiérrez

Crystals 2026, 16(1), 10; https://doi.org/10.3390/cryst16010010 - 24 Dec 2025

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Abstract

Nanocrystalline diamond (NCD) films were synthesized by microwave plasma chemical vapor deposition (MPCVD) from a CH₄/Ar mixture on seedless p-type Si(111) substrates at 100–400 °C. Crystallinity was evaluated by X-ray diffraction (Cu Kα); bonding by Raman spectroscopy and X-ray photoelectron spectroscopy [...] Read more.

Nanocrystalline diamond (NCD) films were synthesized by microwave plasma chemical vapor deposition (MPCVD) from a CH₄/Ar mixture on seedless p-type Si(111) substrates at 100–400 °C. Crystallinity was evaluated by X-ray diffraction (Cu Kα); bonding by Raman spectroscopy and X-ray photoelectron spectroscopy (XPS); morphology and thickness by scanning electron microscopy (SEM); defect states by thermoluminescence (TL). SEM shows continuous films with uniform thickness. XRD displays a broad (111) reflection near 2θ = 44°. Raman and XPS reveal temperature-dependent bonding: between 300 and 400 °C, the sp³ fraction increases relative to sp². TL glow curves show peaks at 157 °C and 270 °C, indicating electron-trap centers. These results demonstrate hydrogen-free and seedless NCD growth at low substrate temperatures, supporting potential electronic and dosimetry applications requiring a low thermal load. Full article

(This article belongs to the Special Issue Advances in Thin-Film Materials and Their Applications)

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14 pages, 2535 KB

Open AccessEditor’s ChoiceArticle

Lanthanide-Induced Local Structural and Optical Modulation in Low-Temperature Ag₂Se

by Sathish Panneer Selvam and Sungbo Cho

Crystals 2026, 16(1), 4; https://doi.org/10.3390/cryst16010004 - 22 Dec 2025

Viewed by 455

Abstract

Low-temperature Ag₂Se is a narrow-band semiconductor, with its transport and optical properties significantly influenced by the local coordination environment. This study investigates the effects of La and Gd incorporation using DFT+U calculations and Ag-K edge EXAFS analysis. Analysis of electron localization [...] Read more.

Low-temperature Ag₂Se is a narrow-band semiconductor, with its transport and optical properties significantly influenced by the local coordination environment. This study investigates the effects of La and Gd incorporation using DFT+U calculations and Ag-K edge EXAFS analysis. Analysis of electron localization function (ELF) and charge density differences reveals increased electron localization at dopant sites. Additionally, k³χ(k) and wavelet transforms demonstrate that the first M-Se shell shifts from approximately 1.346 Å in Ag-Se to around 1.386 Å and 1.291 Å for La-Se and Gd-Se, respectively (phase-uncorrected), thereby confirming dopant-specific lattice distortions while maintaining the orthorhombic framework. The observed changes are associated with an increase in dielectric strength, with ε₂ increasing from approximately 30–40 in pristine Ag₂Se to around 50–60 for La and 70–80 for Gd at low photon energies, alongside enhanced absorption nearing 1.32–1.34 × 10⁵ cm⁻¹. The characteristic plasmon resonance in the range of 15–20 eV is maintained. Rare-earth substitution effectively adjusts local bonding and low-energy optical response in Ag₂Se, with Gd demonstrating the most significant impact among the examined dopants. Full article

(This article belongs to the Special Issue Properties and Synthesis of Luminescent Materials)

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14 pages, 8566 KB

Open AccessEditor’s ChoiceArticle

Lithium Niobate Tantalate Solid Solutions Probed by Luminescence Spectroscopy

by Felix Sauerwein, Niklas Dömer, Tobias Hehemann, Moritz Huesmann, Steffen Ganschow and Mirco Imlau

Crystals 2026, 16(1), 1; https://doi.org/10.3390/cryst16010001 - 19 Dec 2025

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Abstract

The polar oxide Lithium Niobate Tantalate is probed using time-resolved luminescence spectroscopy with the goal of revealing an initial structural insight into the solid solution by analyzing the spectral properties and dynamics of radiatively decaying self-localization phenomena. A blue-green luminescence band can be [...] Read more.

The polar oxide Lithium Niobate Tantalate is probed using time-resolved luminescence spectroscopy with the goal of revealing an initial structural insight into the solid solution by analyzing the spectral properties and dynamics of radiatively decaying self-localization phenomena. A blue-green luminescence band can be induced by ultraviolet nanosecond laser pulses with a temperature-dependent intensity and spectral width, pointing to the radiative decay of optically generated self-trapped excitons as its origin, i.e., electron–hole pairs with strong coupling to either the NbO₆- or TaO₆-octahedra. The luminescence decay takes place in the microsecond time range and deviates significantly from a single exponential behavior, so the determined lifetime constants of up to ≈70 μs and stretching factors (1/3–1/5) are validated in more detail using alternative evaluation methods. We discuss our findings, considering the interplay of radiative and non-radiative decay channels, the transition from self-trapped to free excitons, and the presence of a structural disorder of the oxygen octahedra in the solid solutions. Overall, our results suggest self-trapped excitons as local probes for an initial structural elucidation and provide essential information about further experimental and theoretical studies on the atomic structure of Lithium Niobate Tantalate, but also for improving the crystal quality in the framework of applications in photonics and quantum optics. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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15 pages, 3499 KB

Open AccessEditor’s ChoiceArticle

Photothermal Heat Transfer in Nano-Hydroxyapatite/Carbon Nanotubes Composites Modeled Through Cellular Automata

by Cecilia Mercado-Zúñiga and José Antonio García-Merino

Crystals 2025, 15(12), 1062; https://doi.org/10.3390/cryst15121062 - 17 Dec 2025

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Abstract

Modeling elementary diffusion processes in nanostructured materials is essential for developing platforms capable of interacting with high-speed physical signals. In this work, the photothermal response of a nano-hydroxyapatite/carbon nanotube (nHAp/CNT) composite was experimentally characterized and modeled through a cellular automaton (CA) framework designed [...] Read more.

Modeling elementary diffusion processes in nanostructured materials is essential for developing platforms capable of interacting with high-speed physical signals. In this work, the photothermal response of a nano-hydroxyapatite/carbon nanotube (nHAp/CNT) composite was experimentally characterized and modeled through a cellular automaton (CA) framework designed to capture the thermal propagation of the hybrid system. Synthesizing nHAp/CNT composites enables the combination of the biocompatible and piezoelectric nature of nHAp with the enhanced photothermal response introduced by CNTs. UV–Vis reflectance measurements confirmed that CNT incorporation increases the optical absorption of the ceramic matrix, resulting in more efficient photothermal conversion. The composite was irradiated with a nanosecond pulsed laser, and the resulting thermal transients were compared with CA simulations based on a D2Q9 lattice configuration. The model accurately reproduces experiments, achieving R² > 0.991 and NRMSE below 2.4% for all tested laser powers. This strong correspondence validates the CA approach for predicting spatiotemporal heat diffusion in heterogeneous nanostructured composites. Furthermore, the model revealed a sensitive thermal coupling when two heat sources were considered, indicating synergistic enhancement of local temperature fields. These findings demonstrate both the effective integration of CNTs within the nHAp matrix and the capability of CA-based modeling to describe their photothermal behavior. Overall, this study establishes a computational–experimental basis for designing controlled thermal-wave propagation and guiding future multi-frequency or multi-source photothermal mixing experiments. Full article

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13 pages, 6289 KB

Open AccessEditor’s ChoiceArticle

Chemical Composition and Ultrastructure of Bone Apatite in Initial Osteoporosis: Mineralogical Study

by Artem A. Bibko, Oksana V. Bukharova, Roman Yu. Shendrik, Henry P. Schwarcz, Dmitry V. Lychagin and Evgeni A. Kostrub

Crystals 2025, 15(12), 1057; https://doi.org/10.3390/cryst15121057 - 13 Dec 2025

Viewed by 570

Abstract

Bone is one of the most important organs of mammals, consisting of collagen and apatite. Various diseases, such as osteoporosis, can affect the components of bone tissue, their chemical composition and bone ultrastructure, which leads to changes in properties. In this paper, the [...] Read more.

Bone is one of the most important organs of mammals, consisting of collagen and apatite. Various diseases, such as osteoporosis, can affect the components of bone tissue, their chemical composition and bone ultrastructure, which leads to changes in properties. In this paper, the effect of initial osteoporosis on the chemical composition of bone apatite and the ultrastructure of bone tissue from a mineralogical point of view is analyzed using rat femurs as an example. The chemical composition of bone apatite was studied using SEM, EDS and FTIR-ATR spectroscopy. The bone ultrastructure was examined using a transmission electron microscope. An increase in the content of carbonate ion in the position of the phosphorus group and a change in the orientation of apatite crystals inside mineral plates were revealed against the background of initial osteoporosis, which can affect not only the mechanical properties of bone, but also the stability of apatite under biological conditions. Full article

(This article belongs to the Section Mineralogical Crystallography and Biomineralization)

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18 pages, 20231 KB

Open AccessEditor’s ChoiceArticle

In Situ Alloying of Ti-6Al-7Nb with Copper Using Laser Powder Bed Fusion

by Paul Steinmeier, Kay-Peter Hoyer, Nelson Filipe Lopes Dias, Reiner Zielke, Wolfgang Tillmann and Mirko Schaper

Crystals 2025, 15(12), 1053; https://doi.org/10.3390/cryst15121053 - 12 Dec 2025

Viewed by 427

Abstract

Titanium alloys are widely employed for biomedical implants due to their high strength, biocompatibility, and corrosion resistance, yet their lack of intrinsic antibacterial activity remains a major limitation. Incorporating copper, an antibacterial and β-stabilising element, offers a promising strategy to enhance implant performance. [...] Read more.

Titanium alloys are widely employed for biomedical implants due to their high strength, biocompatibility, and corrosion resistance, yet their lack of intrinsic antibacterial activity remains a major limitation. Incorporating copper, an antibacterial and β-stabilising element, offers a promising strategy to enhance implant performance. This study investigates Ti-6Al-7Nb modified with 1–9 wt.% Cu via in situ alloying during metal-based laser powder bed fusion (PBF-LB/M), with the aim of assessing processability, microstructural evolution, and mechanical properties. Highly dense samples (>99.9%) were produced across all Cu levels, though chemical homogeneity strongly depended on processing parameters. Increasing Cu content promoted β-phase stabilisation, Ti₂Cu precipitation, and pronounced grain refinement. Hardness and yield strength increased nearly linearly with Cu addition, while ductility decreased sharply at ≥5 wt.% Cu due to intermetallic formation, hot cracking, and brittle fracture. These results illustrate both the opportunities and constraints of rapid alloy screening via PBF-LB/M. Overall, moderate Cu additions of 1–3 wt.% provide the most favourable balance between mechanical performance, manufacturability, and potential antibacterial functionality. These findings provide a clear guideline for the design of Cu-functionalised titanium implants and demonstrate the efficiency of in situ alloy screening for accelerated materials development. Full article

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

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18 pages, 4921 KB

Open AccessEditor’s ChoiceArticle

Multi-State Photoluminescence of Donor–π–Acceptor Tetrafluorinated Tolane Mesogenic Dimers in Solution, Crystal, and Liquid-Crystalline Phases

by Sorato Inui, Yuto Eguchi, Masato Morita, Motohiro Yasui, Tsutomu Konno and Shigeyuki Yamada

Crystals 2025, 15(12), 1050; https://doi.org/10.3390/cryst15121050 - 11 Dec 2025

Viewed by 441

Abstract

Photoluminescent liquid crystals with photoluminescence (PL) and liquid-crystalline (LC) properties have attracted attention as PL-switching materials owing to their thermally induced phase transitions, such as crystal → smectic A/nematic → isotropic phase transitions. Our group previously developed tetrafluorinated tolane mesogenic dimers linked by [...] Read more.

Photoluminescent liquid crystals with photoluminescence (PL) and liquid-crystalline (LC) properties have attracted attention as PL-switching materials owing to their thermally induced phase transitions, such as crystal → smectic A/nematic → isotropic phase transitions. Our group previously developed tetrafluorinated tolane mesogenic dimers linked by flexible alkylene-1,n-dioxy spacers, demonstrating that the position of the tetrafluorinated aromatic ring critically influences the LC behavior. However, these compounds exhibited very weak fluorescence owing to an insufficient D–π–A character of the π-conjugated mesogens, which facilitated internal conversion from emissive ππ* to non-emissive πσ* states. We designed and synthesized derivatives in which the mesogen–spacer linkage was modified from ether to ester, thereby enhancing the D–π–A character. Thermal and structural analyses revealed spacer-length parity effects: even-numbered spacers induced nematic phases, whereas odd-numbered spacers stabilized smectic A phases. Photophysical studies revealed multi-state PL across solution, crystal, and LC phases. Strong blue PL (Φ_PL = 0.39–0.48) was observed in solution, while crystals exhibited aggregation-induced emission enhancement (Φ_PL = 0.48–0.77) with spectral diversity. In LC states, Φ_PL values up to 0.36 were maintained, showing reversible intensity and spectral shifts with phase transitions. These findings establish design principles that correlate spacer parity, phase behavior, and PL properties, enabling potential applications in PL thermosensors and responsive optoelectronic devices. Full article

(This article belongs to the Section Liquid Crystals)

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18 pages, 2839 KB

Open AccessEditor’s ChoiceArticle

Experiments and Simulations for Reactive Crystallization of Li₃PO₄ from Low Concentration Li-Rich Brine

by Jie Fan, Wanxia Ma, Xiaoxiang He, Guowang Xu, Zhenghua He, Chaoliang Zhu, Yifei Shi, Bo Li and Xiaochuan Deng

Crystals 2025, 15(12), 1045; https://doi.org/10.3390/cryst15121045 - 8 Dec 2025

Cited by 1 | Viewed by 545

Abstract

Li₃PO₄ is an ideal precursor for synthesizing high-performance LiFePO₄, as it simultaneously provides lithium and phosphorus sources. Extremely low solubility of Li₃PO₄ enables efficient lithium recovery from low-concentration Li-rich brine by reactive crystallization. A focused [...] Read more.

Li₃PO₄ is an ideal precursor for synthesizing high-performance LiFePO₄, as it simultaneously provides lithium and phosphorus sources. Extremely low solubility of Li₃PO₄ enables efficient lithium recovery from low-concentration Li-rich brine by reactive crystallization. A focused beam reflectance measurement (FBRM) system was employed to monitor the key optimization parameters for Li₃PO₄ crystallization, supersolubility, and metastable zone widths (MSZWs). The optimized process parameters were determined by systematically investigating the effects of operating conditions. Additionally, prediction of supersolubility and MSZWs was accomplished with theoretical models. Results demonstrate that both supersolubility and MSZWs exhibit a pronounced negative correlation with temperature. Supersolubility decreased sharply when LiCl concentration exceeded 5 mol·L⁻¹ or Na₃PO₄ concentration surpassed 0.8 mol·L⁻¹. Conversely, it increased exponentially with Na₃PO₄ feeding rate. The effect of impurity (NaCl/KCl) was non-monotonic, initially increasing and then decreasing supersolubility and MSZWs. Among these, Na₂B₄O₇ most significantly enhanced both parameters, followed by Na₂SO₄. The supersolubility data were well-fitted by an empirical equation (R² > 0.99). For MSZWs prediction, the self-consistent Nývlt-like model (R² > 0.9883) and the modified Sangwal’s model (R² > 0.994) achieved superior performance. Collectively, these findings establish a theoretical basis for optimizing lithium recovery via Li₃PO₄ crystallization, facilitating more efficient and sustainable production of high-purity lithium products. Full article

(This article belongs to the Section Crystal Engineering)

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21 pages, 5917 KB

Open AccessEditor’s ChoiceArticle

Enhancing Light Absorption in Perovskite Solar Cells Using Au@Al₂O₃ Core–Shell Nanostructures: An FDTD Simulation Study

by Yunwei Jiang and Congyi Li

Crystals 2025, 15(12), 1023; https://doi.org/10.3390/cryst15121023 - 29 Nov 2025

Cited by 1 | Viewed by 627

Abstract

Adding plasmonic nanostructures to perovskite solar cells (PSCs) can boost light absorption, but often at the cost of new electronic losses. Based on 3D FDTD simulations, this study demonstrates how Au@Al₂O₃ core-shell nanostructures can overcome this fundamental trade-off through a [...] Read more.

Adding plasmonic nanostructures to perovskite solar cells (PSCs) can boost light absorption, but often at the cost of new electronic losses. Based on 3D FDTD simulations, this study demonstrates how Au@Al₂O₃ core-shell nanostructures can overcome this fundamental trade-off through a dual function of the Al₂O₃ shell, namely its moderate refractive index and excellent passivating properties. In addition, the geometry of Au@Al₂O₃ core–shell nanostructure is optimized to produce a maximum short-circuit current density (

J_{s c}

) of 25 mA cm⁻². The simulations provide mechanism-level design rules that link dielectric choice and geometry to near-field localization and far-field coupling in perovskite absorbers. An experimentally testable parameter window is reported rather than device-level performance claims, with explicit discussion of energy partitioning and stability caveats associated with plasmonic loss in Au and interfacial chemistry. Full article

(This article belongs to the Section Materials for Energy Applications)

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27 pages, 16914 KB

Open AccessEditor’s ChoiceReview

Graphene Imaging Using Scanning Electron Microscopy: Mechanism of Secondary Electron Contrast Formation

by Yoshikazu Homma

Crystals 2025, 15(12), 1025; https://doi.org/10.3390/cryst15121025 - 29 Nov 2025

Viewed by 860

Abstract

For growth control of graphene, observation techniques, particularly those allowing in situ imaging during synthesis, are essential. Scanning electron microscopy (SEM) is a conventional surface observation method capable of in situ imaging of graphene segregation or growth in chemical vapor deposition, as well [...] Read more.

For growth control of graphene, observation techniques, particularly those allowing in situ imaging during synthesis, are essential. Scanning electron microscopy (SEM) is a conventional surface observation method capable of in situ imaging of graphene segregation or growth in chemical vapor deposition, as well as ex situ imaging of synthesized materials. However, secondary electron (SE) emission from graphene is not fully understood, and the contrast formation mechanism of the monolayer material remains unclear. This review summarizes the SEM imaging of graphene, with a focus on SE contrast mechanisms under different conditions. The monolayer graphene layer does not greatly affect SE emission. Its SE contrast is brought from the charging effect, oxidation effect, or attenuation effect of backscattered electron (BSE) from the substrate. Characteristics of SE detectors, such as energy window, acceptance angle, and detected SE/BSE ratio, also contribute to the graphene contrast formation. Full article

(This article belongs to the Special Issue Advanced Technologies in Graphene-Based Materials (2nd Edition))

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15 pages, 7214 KB

Open AccessEditor’s ChoiceArticle

Influence of the Monodentate Coordination of Biphenyl Carboxylic Acid Isomers on the Luminescent Properties of Mononuclear Europium Complexes

by Carlos Felipe Hernández-Fuentes, Ángel de Jesús Morales-Ramírez, Luis Sergio Cuevas-Cadena, María Luz Carrera-Jota, Ciro Falcony-Guajardo, José Ortíz-Landeros, Adán Ramírez-López and Juan Alberto Alcántara Cárdenas

Crystals 2025, 15(12), 1028; https://doi.org/10.3390/cryst15121028 - 29 Nov 2025

Viewed by 467

Abstract

This study presents the synthesis, crystal structure determination and luminescence properties of three novel mononuclear europium (III) complexes constructed from sodium benzoate and the three different isomers of biphenylcarboxylic acid (2-, 3-, and 4-). All complexes share a common structural core; consisting of [...] Read more.

This study presents the synthesis, crystal structure determination and luminescence properties of three novel mononuclear europium (III) complexes constructed from sodium benzoate and the three different isomers of biphenylcarboxylic acid (2-, 3-, and 4-). All complexes share a common structural core; consisting of a single europium (III) ion coordinated by three bidentate benzoate ligands and two monodentate biphenylcarboxylate ligands. The synthesis followed a two-step strategy: first, a benzoate-based precursor complex was prepared by displacing the chloride and water molecules from europium (III) chloride hexahydrate with sodium benzoate by chelating process. The remaining water ligands were substituted with each biphenylcarboxylic acid isomer yielding solvent-free luminescent complexes. The structural characterization involved thermogravimetric analysis (TGA) to confirm the complete elimination of water molecules. The crystal structures of the europium (III) complexes were solved from X-ray powder diffraction data using the EXPO2014 software; and were deposited in the Cambridge Crystallographic Data Centre (CCDC) under deposition numbers 2477668, 2477667 and 2476992. The photoluminescence properties, including excitation, emission, decay time, and color purity, were studied. The influence of each biphenylcarboxylate isomer on the symmetry of the europium coordination sphere was assessed by calculating the asymmetry ratio, R = (I⁵D₀ → ⁷F₂/I⁵D₀ → ⁷F₁), revealing clear differences in emission intensity and symmetry distortion, directly correlated to the ligand isomer used. These findings demonstrate the antenna effect and tunable luminescence enabled by ligand design, offering potential applications in optoelectronics, bio-imaging and others. Full article

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13 pages, 2722 KB

Open AccessEditor’s ChoiceArticle

2D Organic–Inorganic Halide Perovskites for Hybrid Heterostructures: Single Crystals, Thin Films and Exfoliated Flakes

by Fabrizio Ciccarelli, Mario Barra, Antonio Carella, Gabriella Maria De Luca, Felice Gesuele and Fabio Chiarella

Crystals 2025, 15(12), 1024; https://doi.org/10.3390/cryst15121024 - 29 Nov 2025

Viewed by 628

Abstract

Rapid progress on the fabrication of lead halide perovskite has led to the development of high performance optoelectronic devices, particularly in the field of solar cell technologies. This initial success has subsequently inspired investigations into layered 2D-halide perovskite structures, motivated in part by [...] Read more.

Rapid progress on the fabrication of lead halide perovskite has led to the development of high performance optoelectronic devices, particularly in the field of solar cell technologies. This initial success has subsequently inspired investigations into layered 2D-halide perovskite structures, motivated in part by their good environmental stability, but more significantly by their intriguing fundamental photo-physics. They have recently been used to improve the photoresponsivity of monolayer transition metal dichalcogenides in hybrid heterostructures. In this paper, we report on the synthesis of the (PEA)₂(MA)_n₋₁Pb_nI_3n+1 series (with n = 1, 2, 3) of 2D-halide perovskites, in order to develop a platform that provides ultra-thin layers for the fabrication of hybrid heterostructures. The crystal synthesis method and its basic structural and optical characterization are shown, highlighting the differences in the crystal synthesis processes. Furthermore, we explore the preparation of 2D halide perovskite ultra-thin flakes using the mechanical exfoliation method, and few-layer-areas of n = 1 member of the series are identified using atomic force microscopy. Finally, we study the deposition of thin and ultra-thin films using the spin coating technique to provide an alternative process to the exfoliation. Full article

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13 pages, 3475 KB

Open AccessEditor’s ChoiceArticle

3D Study of Microstructural Influences on Retained Austenite Transformation in Q&P 1180 Steel

by Isaac Chelladurai, Emily V. White, Michael P. Miles, Eric R. Homer, Anil K. Sachdev and David T. Fullwood

Crystals 2025, 15(12), 1015; https://doi.org/10.3390/cryst15121015 - 25 Nov 2025

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Abstract

Advanced TRIP steels offer an attractive combination of strength and ductility because of the transformation-induced plasticity (TRIP) phenomenon. The retained austenite (RA) embedded in quenched and partitioning (Q&P) 1180 steel provides vital ductility, relating to the propensity of these grains to transform under [...] Read more.

Advanced TRIP steels offer an attractive combination of strength and ductility because of the transformation-induced plasticity (TRIP) phenomenon. The retained austenite (RA) embedded in quenched and partitioning (Q&P) 1180 steel provides vital ductility, relating to the propensity of these grains to transform under applied deformation. It is well known that the characteristics of the RA grains (size, shape, orientation, etc.) have a strong influence on their stability, but few studies consider the accurate 3-dimensional character of the grains, due to the cost of extracting 3D data. This study observes the characteristics of RA grains in Q&P 1180 steel before and after applying tensile deformation. EBSD maps of serial sectioned layers are reconstructed using DREAM3D. The influence of 3D morphology and other factors on transformation of RA is studied. Apart from relatively traditional metrics, a novel shear affinity factor is introduced as a metric to describe the ease of transformation for an RA grain. The 3D nature of the information collected allows accurate classification of grain shape into the traditional globular/spherical and lamellar/lath categories, along with disk and needle shapes, and enables quantification of the evolution of the shape distributions. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Behavior of Advanced High Strength Steels)

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14 pages, 5937 KB

Open AccessEditor’s ChoiceArticle

Variation in Carbon Content During the Melting of γ-TiAl in a Graphite Crucible

by Byungil Kang, Taekyu Ha, Seul Lee and Youngjig Kim

Crystals 2025, 15(12), 1006; https://doi.org/10.3390/cryst15121006 - 22 Nov 2025

Cited by 1 | Viewed by 2329

Abstract

Liquid γ-TiAl alloy was prepared by vacuum induction melting within graphite crucibles, then cast using a centrifugal technique. In this process, the degree of superheat (ΔT)—defined as the temperature above the melting point—was carefully controlled, with experiments conducted at ΔT of 200 K [...] Read more.

Liquid γ-TiAl alloy was prepared by vacuum induction melting within graphite crucibles, then cast using a centrifugal technique. In this process, the degree of superheat (ΔT)—defined as the temperature above the melting point—was carefully controlled, with experiments conducted at ΔT of 200 K (i.e., 200 Kelvin above the melting temperature). It was observed that carbon content in the alloy increased nonlinearly as the melt was held longer in the graphite crucible; for example, carbon concentration rose from an initial value of approximately 0.21 at% to 0.98 at% after 100 s of holding and to 2.11 at% at 650 s of holding. When the melt was held for over 100 s at ΔT = 200 K, titanium carbide (TiC) and titanium aluminum carbide (Ti₂AlC) particles formed along the crucible wall. This resulted in changes to the phase fractions and a corresponding increase in aluminum concentration in the melt. Two types of Ti₂AlC phases were observed: one consisted of coarse Ti₂AlC particles, which were crystallized through peritectic reaction from the TiC carbide and liquid phase. The other consisted of fine Ti₂AlC particles, which were decomposed from the α₂ (Ti₃Al) phase within the interlamellar regions. After 20 s of holding at ΔT = 200 K, carbon rapidly dissolved into a solid solution. Prolonged holding led to significant grain refinement: the microstructure evolved from columnar to equiaxed grains, primarily due to TiC crystallization. This transition is significant because finer, equiaxed grains can enhance mechanical properties such as strength and toughness. The findings provide valuable insight into the interaction between graphite crucibles and γ-TiAl melts, demonstrating how controlled superheat and holding time influence carbon uptake, carbide formation, and microstructural evolution—factors critical for optimizing the performance and manufacturability of γ-TiAl components. Full article

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13 pages, 3069 KB

Open AccessEditor’s ChoiceArticle

Boosting Charge Separation in NiS/C₃N₄ Type-II Heterojunction for Efficient Photoelectrocatalytic Water Reduction

by Xiaobo Liang, Lingdan Dong, Yanning Chen, Chunhai Qi, Chunyi Xu, Wenhao Zhang, Lingling Bi and Liang Zhao

Crystals 2025, 15(12), 1004; https://doi.org/10.3390/cryst15121004 - 21 Nov 2025

Viewed by 412

Abstract

To tackle the intrinsic limitations of fast charge recombination and sluggish reaction kinetics in carbon nitride (C₃N₄) for photoelectrocatalytic (PEC) water reduction reaction, we constructed a NiS/C₃N₄ heterojunction photoelectrode via a sequential approach combining chemical vapor [...] Read more.

To tackle the intrinsic limitations of fast charge recombination and sluggish reaction kinetics in carbon nitride (C₃N₄) for photoelectrocatalytic (PEC) water reduction reaction, we constructed a NiS/C₃N₄ heterojunction photoelectrode via a sequential approach combining chemical vapor deposition and hydrothermal treatment. Compared with pristine C₃N₄, the introduction of NiS significantly reduced interfacial charge transfer resistance and effectively suppressed the photogenerated carrier recombination. Among all compositions investigated, the NiS-0.2 photoelectrode demonstrated a maximum photocurrent density of −13.44 mA cm⁻² at −0.8 V vs. RHE, representing a more than 6.7-fold enhancement in comparison to bare C₃N₄ (−2.00 mA cm⁻²). This remarkable improvement is attributed to the construction of an efficient type-II heterojunction between C₃N₄ and NiS. Under the driving force of the internal electric field at the interface, photoinduced electrons migrate from the conduction band of C₃N₄ to NiS, whereas holes move from the valence band of NiS to C₃N₄. This spatial separation mechanism, coupled with the role of NiS as an efficient active site for the water reduction reaction, synergistically enhances the overall PEC performance. This work offers a rational and feasible approach for designing efficient, stable, and cost-effective C₃N₄-based photoelectrodes. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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13 pages, 3846 KB

Open AccessEditor’s ChoiceArticle

Novel 2D Porous Metal–Organic Frameworks: Synthesis, X-Ray Structure, Thermal, and Hirshfeld Surface Analyses

by Rupam Sen, Mahananda Roy, Sriparna Sanyal, Arpan Dolui, Paula Brandão and Zhi Lin

Crystals 2025, 15(11), 989; https://doi.org/10.3390/cryst15110989 - 15 Nov 2025

Viewed by 616

Abstract

In the present study, we have developed a series of compounds [M(tcm)₂(bix)₄]_n [where M = Co (1), Ni (2), and Cu (3)] using tricyanomethanide (tcm) and 1,4-bis(imidazol-1-ylmethyl)benzene (bix) ligands. The compounds were [...] Read more.

In the present study, we have developed a series of compounds [M(tcm)₂(bix)₄]_n [where M = Co (1), Ni (2), and Cu (3)] using tricyanomethanide (tcm) and 1,4-bis(imidazol-1-ylmethyl)benzene (bix) ligands. The compounds were characterized by elemental analysis, PXRD, FT-IR and single-crystal X-ray crystallography. Single-crystal X-ray investigation of compounds 1, 2, and 3 shows the formation of the porous 2D structure. These 2D structures are further stacked to create a 3D network in the crystallographic space. All the compounds are thermally stable up to 300 °C, as revealed by the TGA. Hirshfeld surface analysis was carried out, and it reveals the existence of short intermolecular interactions between the layers. 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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17 pages, 3178 KB

Open AccessEditor’s ChoiceArticle

Laser-Synthesized Plasmono-Fluorescent Si-Au and SiC-Au Nanocomposites for Colorimetric Sensing

by Yury V. Ryabchikov

Crystals 2025, 15(11), 982; https://doi.org/10.3390/cryst15110982 - 14 Nov 2025

Viewed by 932

Abstract

Sensing represents one of the most rapidly developing areas of modern life sciences, spreading from the detection of pathogenic microorganisms in living systems, food, and beverages to hazardous substances in liquid and gaseous environments. However, the development of efficient and low-cost multimodal sensors [...] Read more.

Sensing represents one of the most rapidly developing areas of modern life sciences, spreading from the detection of pathogenic microorganisms in living systems, food, and beverages to hazardous substances in liquid and gaseous environments. However, the development of efficient and low-cost multimodal sensors with easy-to-read functionality is still very challenging. In this paper, stable aqueous colloidal suspensions (ζ-potential was between −30 and −40 mV) of ultrasmall (~7 nm) plasmonic Si-Au and SiC-Au nanocomposites were formed. Two variants of pulsed laser ablation in liquids (PLAL)—direct ablation and laser co-fragmentation—were used for this purpose. The co-fragmentation approach led to a considerable decrease in hydrodynamic diameter (~78 nm) and bandgap widening to approximately 1.6 eV. All plasmonic nanocomposites exhibited efficient multi-band blue emission peaking at ~430 nm upon Xe lamp excitation. Co-fragmentation route considerably (~1 order of magnitude) increased the PL efficiency of the nanocomposites in comparison with the laser-ablated ones, accompanied by a negligible amount of dangling bonds. These silicon-based nanostructures significantly affected the optical response of rhodamine 6G, depending on the synthesis route. In particular, directly ablated nanoparticles revealed a stronger influence on the optical response of dye molecules. The observed findings suggest using such types of semiconductor-plasmonic nanocomposites for multimodal plasmonic and colorimetric sensing integrated with luminescent detection capability. Full article

(This article belongs to the Special Issue Synthesis, Characterization and Applications of Multi-Component Hybrid and Composite Nanostructures)

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14 pages, 2965 KB

Open AccessEditor’s ChoiceArticle

Study on Microstructure Evolution and Influencing Factors of Pure Copper Wire After Directional Heat Treatment

by Hao Xu, Xin Dong, Feixiang Chen, Yang Chen and Guang Chen

Crystals 2025, 15(11), 984; https://doi.org/10.3390/cryst15110984 - 14 Nov 2025

Cited by 1 | Viewed by 555

Abstract

The Ohon Continuous Casting is the main method for preparing single crystal copper wire, and it is also the research hotspot at present, but it is difficult to directly cast ultrafine single crystal copper wire (diameter < 0.05 mm). The copper wire obtained [...] Read more.

The Ohon Continuous Casting is the main method for preparing single crystal copper wire, and it is also the research hotspot at present, but it is difficult to directly cast ultrafine single crystal copper wire (diameter < 0.05 mm). The copper wire obtained by continuous casting must be drawn and deformed before it can be used in practice, but this will bring a series of problems such as single crystal structure destruction and conductivity deterioration. Directional heat treatment technology can control the direction of heat flow at a low temperature, realize the directional migration of grain boundaries in the recrystallization process, and form columnar crystals or single crystals, which is of great significance for improving electrical conductivity. In this paper, the directional heat treatment method was used to investigate the microstructure evolution and influencing factors of pure copper wire, the process parameters were optimized, and the conductivity of pure copper wire was measured. It was found that the conductivity of pure copper wire increased by 5% when the heating temperature was 750 °C and the withdrawing velocity was 15 μm/s, which laid a foundation for the improvement of conductivity of pure copper wire. Full article

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

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18 pages, 11078 KB

Open AccessEditor’s ChoiceArticle

Mechanism of Hydrothermal Zeolite Crystallization from Kaolin in Concentrated NaOH Solutions (1–5 M): Formation of NaP1, NaP2, Analcime, Sodalite and Cancrinite

by Paola Mameli, Ambra M. Fiore, Saverio Fiore and F. Javier Huertas

Crystals 2025, 15(11), 980; https://doi.org/10.3390/cryst15110980 - 14 Nov 2025

Cited by 2 | Viewed by 861

Abstract

Kaolin from the Donigazza deposit (NW Sardinia, Italy) was used to investigate the mechanisms of zeolite crystallization under alkaline hydrothermal conditions. The starting material, composed mainly of kaolinite and opal-CT with minor quartz and low iron content, was reacted with NaOH solutions (1–5 [...] Read more.

Kaolin from the Donigazza deposit (NW Sardinia, Italy) was used to investigate the mechanisms of zeolite crystallization under alkaline hydrothermal conditions. The starting material, composed mainly of kaolinite and opal-CT with minor quartz and low iron content, was reacted with NaOH solutions (1–5 mol L⁻¹) at 100 °C for 12–168 h. XRD analyses revealed the formation of zeolitic and related phases, including NaP1, NaP2, analcime, sodalite, and cancrinite, with zeolite contents reaching up to 100%. The extent of kaolinite dissolution varied with both NaOH concentration and reaction time, with complete transformation occurring at ≥3 mol L⁻¹ and ≥48 h. SEM imaging showed idiomorphic crystals (100 nm–10 μm) and globular nanoparticles (<50 nm), likely Na-Al-Si gels. Phase distribution reflected evolving solution chemistry, particularly changes in the Si/Al ratio due to differential dissolution of opal-CT and kaolinite. Crystallization proceeded via both classical (monomer addition) and non-classical (particle attachment) pathways, influenced by supersaturation, gel composition, and reaction kinetics. The transition from NaP1 to NaP2, and the development of metastable phases, indicate kinetic control consistent with Ostwald’s step rule. These results provide insights into the complex dynamics of zeolite formation from natural aluminosilicate precursors in alkaline environments. Full article

(This article belongs to the Special Issue Crystal Structure and Characterization of Minerals and Related Nanomaterials)

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21 pages, 3742 KB

Open AccessEditor’s ChoiceArticle

Stability of Higher-Order Skyrmion Crystals Under Competing Magnetic Anisotropies in D_3d Systems

by Satoru Hayami

Crystals 2025, 15(11), 978; https://doi.org/10.3390/cryst15110978 - 13 Nov 2025

Viewed by 943

Abstract

We investigate the stability of higher-order skyrmion crystals with large topological charges in the presence of crystal-dependent magnetic anisotropies. Focusing on the competition between two types of bond-dependent anisotropy allowed by

D_{3 d}

crystalline symmetry on a two-dimensional triangular lattice, we systematically [...] Read more.

We investigate the stability of higher-order skyrmion crystals with large topological charges in the presence of crystal-dependent magnetic anisotropies. Focusing on the competition between two types of bond-dependent anisotropy allowed by

D_{3 d}

crystalline symmetry on a two-dimensional triangular lattice, we systematically construct a low-temperature magnetic phase diagram using simulated annealing. Our analysis reveals that the stability of the higher-order skyrmion crystal with skyrmion number of two is strongly controlled by the relative sign of the bond-dependent anisotropy to the

D_{3 d}

-type anisotropy: a positive anisotropy, which favors spin oscillations perpendicular to the ordering wave vector, enhances its stability, whereas a negative anisotropy, favoring oscillations parallel to the ordering wave vector, suppresses it and instead stabilizes a topologically trivial double-Q state. We further examine the field evolution of these phases under an out-of-plane magnetic field and show that distinct types of skyrmion crystals with the skyrmion number of one emerge in the intermediate-field regime. These results highlight that the competition between different magnetic anisotropies in crystalline systems is a key factor governing the stability of both zero-field and field-induced skyrmion crystals. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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22 pages, 20191 KB

Open AccessEditor’s ChoiceArticle

Effect of Tungsten Content on the Microstructure, Mechanical and Tribological Properties of AlCoCrFeNi High-Entropy Alloys

by Ersin Bahceci, Ali Oktay Gul, Oykum Basgoz Orhan, Levent Cenk Kumruoglu and Omer Guler

Crystals 2025, 15(11), 972; https://doi.org/10.3390/cryst15110972 - 12 Nov 2025

Viewed by 748

Abstract

High-entropy alloys (HEAs) have recently attracted considerable attention due to their unique combination of high strength, hardness, and corrosion and wear resistance, making them promising candidates for advanced structural and functional applications. Among these, AlCoCrFeNi-based HEAs are well known for their high hardness [...] Read more.

High-entropy alloys (HEAs) have recently attracted considerable attention due to their unique combination of high strength, hardness, and corrosion and wear resistance, making them promising candidates for advanced structural and functional applications. Among these, AlCoCrFeNi-based HEAs are well known for their high hardness and good wear resistance; however, their limited tribological stability under operational conditions restricts their broader application. To address this limitation, tungsten (W) was incorporated into the AlCoCrFeNi system to enhance its mechanical and tribological performance. In this study, the microstructural, mechanical, and tribological properties of AlCoCrFeNiW_x (x = 0, 0.1, 0.25, 0.5 and 1 mol) HEAs were systematically investigated. The alloys were fabricated using the vacuum arc melting method and characterized by XRD, SEM-EDS, elemental mapping, microhardness, and wear tests. The addition of W caused a shift in the 2θ ≈ 44° (110) peak toward lower angles. While the W-free alloy exhibited Body-Centered Cubic (BCC) + B2 phases, W addition led to the formation of a new W-rich phase, and at higher W contents, a pure W phase appeared. The hardness increased from 507.11 HV₁ to 651.81 HV₁ with increasing W content. Furthermore, wear resistance improved and the coefficient of friction decreased with higher W addition. When comparing the W-free alloy to the alloy with the highest W content, the wear rate decreased by approximately 1.85 times under a 2 N load and 1.89 times under a 5 N load. These results demonstrate that W addition significantly enhances the wear resistance of AlCoCrFeNi-based HEAs by nearly twofold. Full article

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

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16 pages, 3946 KB

Open AccessEditor’s ChoiceArticle

Tribological Behavior of SPS-Prepared Al-Matrix–ZrO₂-Nanofiber Composites with Graphene Nanoplatelets Solid-Lubricating Surface Films

by Viktor Puchý, Richard Sedlák, Marek Vojtko, Mária Podobová, Ondrej Petruš, Lucia Čiripová and Ladislav Falat

Crystals 2025, 15(11), 971; https://doi.org/10.3390/cryst15110971 - 12 Nov 2025

Viewed by 422

Abstract

In this study, the tribological compatibility of ZrO₂-nanofiber-strengthened Al-matrix composites with graphene nanoplatelets (GNPs)-derived surface film acting as a solid lubricant was investigated. The substrate materials prepared by Spark Plasma Sintering (SPS) included the pure aluminum monolith (reference material) and two [...] Read more.

In this study, the tribological compatibility of ZrO₂-nanofiber-strengthened Al-matrix composites with graphene nanoplatelets (GNPs)-derived surface film acting as a solid lubricant was investigated. The substrate materials prepared by Spark Plasma Sintering (SPS) included the pure aluminum monolith (reference material) and two Al–ZrO₂ nanocomposites with either 1 or 3 wt.% of ZrO₂ nanofibers. The GNPs-derived solid lubricant films were dry mechanically burnished into the metallographically polished surfaces. The durability of these burnished films was evaluated by performing tribological friction experiments using a ball-on-disk method. Thus, a friction load capacity of GNP-derived tribofilms on the substrate materials and its effect on the coefficient of friction (COF) were evaluated. The results showed that the films burnished on the surfaces of Al–ZrO₂ nanofiber composites were more resistant to much higher loads than films burnished on monolithic aluminum. The obtained findings indicated that ZrO₂ nanofiber protrusions likely stabilize a GNP-derived carbon tribolayer on the polished composite surfaces. As a result, the reinforcement of aluminum with ceramic nanofibers led also to a significant reduction in COF. The highest improvement of tribological performance was observed for the Al–ZrO₂ nanofiber composite with 1 wt.% ZrO₂ nanofibers. The increase of ZrO₂ nanofibers up to 3 wt.% was no more efficient due to nanofiber clustering leading to lower stability of the carbon friction film. Our objective was to isolate the role of the aluminum substrate, specifically, ZrO₂ nanofiber protrusions in the formation and retention of a GNP-derived carbon tribofilm under room-temperature, ambient-air dry sliding. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

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23 pages, 38358 KB

Open AccessEditor’s ChoiceArticle

Microstructure and Mechanical Properties of Hybrid Pure Al/B₄C/Microsilica Composites Produced by Ultrasonically Assisted Stir Casting

by Maxat Abishkenov, Ilgar Tavshanov, Kairosh Nogayev, Zoja Gelmanova, Saule Kamarova and Almas Yerzhanov

Crystals 2025, 15(11), 973; https://doi.org/10.3390/cryst15110973 - 12 Nov 2025

Viewed by 555

Abstract

This study explores the fabrication and characterization of hybrid aluminum matrix composites reinforced with boron carbide (B₄C) and microsilica, produced via ultrasonically assisted stir casting followed by T6 heat treatment. Pure aluminum was selected as the base matrix to evaluate the [...] Read more.

This study explores the fabrication and characterization of hybrid aluminum matrix composites reinforced with boron carbide (B₄C) and microsilica, produced via ultrasonically assisted stir casting followed by T6 heat treatment. Pure aluminum was selected as the base matrix to evaluate the combined effects of B₄C and microsilica reinforcements. Microstructural analyses showed that ultrasonic treatment effectively dispersed nanoparticles, reduced agglomeration, and enhanced particle–matrix interfacial bonding. T6 heat treatment further refined the grain structure through Zener pinning and promoted the formation of reaction layers at particle interfaces. Mechanical testing revealed that Al/B₄C composites provided the highest strength and hardness, while Al/microsilica systems retained superior ductility. The hybrid Al/B₄C/microsilica composites demonstrated a balanced combination of yield strength (38.6 MPa), ultimate tensile strength (82.6 MPa), and elongation (35.2%), confirming a synergistic strengthening–toughening effect. These results highlight the potential of Al/B₄C/microsilica hybrid reinforcements to optimize the trade-off between strength and ductility in aluminum-based composites. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

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11 pages, 5414 KB

Open AccessEditor’s ChoiceArticle

Characterization of Cobalt-Based Composite Multilayer Laser-Cladded Coatings

by Iasmina-Mădălina Anghel, Alexandru Pascu, Iosif Hulka, Dino Horst Woelk, Ion-Dragoș Uțu and Gabriela Mărginean

Crystals 2025, 15(11), 970; https://doi.org/10.3390/cryst15110970 - 11 Nov 2025

Cited by 3 | Viewed by 633

Abstract

Laser cladding is an essential method for strengthening and restoring component surfaces. To increase its efficacy and provide a reliable surface treatment technique, it is necessary to optimize process parameters, enhance material adhesion, and guarantee high-quality, reliable coatings. These measures help to extend [...] Read more.

Laser cladding is an essential method for strengthening and restoring component surfaces. To increase its efficacy and provide a reliable surface treatment technique, it is necessary to optimize process parameters, enhance material adhesion, and guarantee high-quality, reliable coatings. These measures help to extend the lifespan of components. In this study, the surfaces of AISI 904L stainless steel samples were cladded to prepare various Co-based composite coatings with single and multiple layers reinforced with WC–CoCr–Ni powder. The phases within the newly developed layers were investigated using X-ray Diffraction (XRD), while the microstructure was examined using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX). Further tests were performed to assess the hardness, wear resistance and corrosion performance of the deposited coatings. Analyzing and comparing the coatings, it was observed that the coating performance increased with increasing thickness and generally due to a lower amount of Fe present within the microstructure. Full article

(This article belongs to the Special Issue Crystallization of High Performance Metallic Materials (2nd Edition))

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17 pages, 1889 KB

Open AccessEditor’s ChoiceArticle

Zinc(II) Iodide Complexes with Redox-Active α-Diimine Ligands: Synthesis, Structure, Spectroscopic and Electrochemical Properties

by Dmitriy S. Yambulatov, Natalia V. Gogoleva, Ivan V. Smolyaninov, Vladimir A. Bushuev, Anna A. Tychinina, Alexandra S. Samulionis, Julia K. Voronina, Ivan V. Skabitsky, Sergey S. Shapovalov, Stanislav A. Nikolaevskii and Mikhail A. Kiskin

Crystals 2025, 15(11), 967; https://doi.org/10.3390/cryst15110967 - 10 Nov 2025

Viewed by 683

Abstract

Reactions of anhydrous Zn(II) iodides with redox-active 1,4-diaza-1,3-butadiene (DAD) and its bis(imino)acenaphtene (BIAN) derivatives in absolute acetonitrile yielded a series of new complexes: [(Mes-DAD)ZnI₂] (1), [(dpp-DAD)ZnI₂] (2), and [(dpp-BIAN)ZnI₂] (3). Single [...] Read more.

Reactions of anhydrous Zn(II) iodides with redox-active 1,4-diaza-1,3-butadiene (DAD) and its bis(imino)acenaphtene (BIAN) derivatives in absolute acetonitrile yielded a series of new complexes: [(Mes-DAD)ZnI₂] (1), [(dpp-DAD)ZnI₂] (2), and [(dpp-BIAN)ZnI₂] (3). Single crystals of all compounds were obtained, and their molecular structures were unambiguously determined by X-ray diffraction analysis. Purity of bulk samples in solid state was confirmed by PXRD. Stability of the complexes in solution was investigated by means of UV-Vis and NMR spectroscopy. Cyclic voltammetry revealed two or three quasi-reversible reduction waves in the cathodic region for complexes 1–3. The ability of 3 to accept up to three electrons highlights the potential of these compounds as electrocatalysts for reductive transformations. Full article

(This article belongs to the Special Issue Transition Metal Complexes with Heterocyclic Ligands: Structural Insights, Biological Potential, and Computational Perspectives)

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19 pages, 3894 KB

Open AccessFeature PaperEditor’s ChoiceReview

The Crystallography of Enzymes: A Retrospective and Beyond

by Tianyi Huang, Jannat Khan, Sheryar Lakhani, Albert Li, Aditya Vyas, Julia Hunt, Sara Andrea Espinosa Garcia and Bo Liang

Crystals 2025, 15(11), 966; https://doi.org/10.3390/cryst15110966 - 8 Nov 2025

Viewed by 1632

Abstract

Crystallography plays a crucial role in understanding the functions of macromolecules by determining their three-dimensional structures at the atomic level. This review outlines the history of crystallization, explains the principles of crystallization, and provides a comprehensive retrospective on the role of crystallography in [...] Read more.

Crystallography plays a crucial role in understanding the functions of macromolecules by determining their three-dimensional structures at the atomic level. This review outlines the history of crystallization, explains the principles of crystallization, and provides a comprehensive retrospective on the role of crystallography in enzymology, with a particular focus on the seven Enzyme Commission (EC) classes. For each class, we highlight representative enzymes and the specific mechanistic insights enabled by crystal structures, oxidoreductases (the “yellow enzyme” lineage), transferases (phosphotransferase systems), hydrolases (RNase III and chymotrypsin), lyases (fumarase), isomerases (pseudouridine synthases), ligases (E3 ubiquitin ligases), and translocases (ATP synthase), emphasizing cofactor usage, conformational change, regulation, and implications for disease and drug discovery. We also compile EC-wide statistics from the Protein Data Bank (PDB) to quantify structural coverage. The limitations and challenges of current crystallization techniques are addressed, along with alternative experimental methods for structural elucidation. In addition, emerging computational tools and biomolecular design are also discussed. By reviewing the trajectory of enzymology and crystallography, we demonstrated their profound impact on biochemistry and therapeutic discovery. Full article

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

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17 pages, 3558 KB

Open AccessEditor’s ChoiceArticle

Single Crystal X-Ray Structure Determination and Vibrational Spectroscopy of 2-Aminopyrimidinium Hydrogen Trioxofluorophosphate and bis(2-Aminopyrimidinium) Trioxofluorophosphate

by Irena Matulková, Jan Fábry and Ivana Císařová

Crystals 2025, 15(11), 952; https://doi.org/10.3390/cryst15110952 - 3 Nov 2025

Viewed by 420

Abstract

Two single-crystal X-ray structure determinations of 2-aminopyrimidinium hydrogen tri oxofluorophosphate, (C₄H₆N₃)⁺·(HFO₃P)⁻, (I), and bis(2-aminopyrimidinium) trioxofluorophosphate, 2(C₄H₆N₃)⁺·(FO₃P)²⁻, (II), as well [...] Read more.

Two single-crystal X-ray structure determinations of 2-aminopyrimidinium hydrogen tri oxofluorophosphate, (C₄H₆N₃)⁺·(HFO₃P)⁻, (I), and bis(2-aminopyrimidinium) trioxofluorophosphate, 2(C₄H₆N₃)⁺·(FO₃P)²⁻, (II), as well as their vibration spectra (FTIR on powder samples and the Raman spectra on unoriented single crystals) with a detailed assignment of vibrational modes are reported. The structure (I) consists of one independent 2-aminopyrimidinium cation and one hydrogen trioxofluorophosphate anion, while (II) consists of two symmetry independent 2-aminopyrimidinium cations and one trioxofluorophosphate anion. In (I), there is an O-H···O hydrogen bond of a moderate strength. A pair of these hydrogen bonds is situated about the symmetry centre and involved in the graph set motif R²₂(8). There are also N-H···O hydrogen bonds of a moderate strength, which are present in both structures while being involved in the graph set motifs R²₂(8), too. In addition, the N-H···O hydrogen bonds form R³₄(10) graph set motifs in (II). The latter motifs form ribbons which propagate parallel to the unit-cell axis a. In both structures, there are present π···π-electron ring interactions into which the primary amine groups are involved. In both structures, there are also present weak C-H···N hydrogen bonds with participation of the non-protonated ring N-atoms. The fluorine participates in the C-H···F hydrogen bonds in both title structures. The P-F distances are normal in both anions. The structure (I) differs from the known structure of 2-aminopyrimidinium hydrogen phosphite, the compositional isomer, though the main hydrogen bonds show similar geometry in both structures. The crystal of (I) was twinned. Full article

(This article belongs to the Section Organic Crystalline Materials)

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17 pages, 2210 KB

Open AccessEditor’s ChoiceArticle

The Preparation and Properties of Polycrystalline Bi₂O₂Se—Pitfalls in Reproducibility and Charge-Transport Limiting Factors

by Jan Zich, Tomáš Plecháček, Antonín Sojka, Petr Levinský, Jiří Navrátil, Pavlína Ruleová, Stanislav Šlang, Karel Knížek, Jiří Hejtmánek, Vojtěch Nečina and Čestmír Drašar

Crystals 2025, 15(11), 951; https://doi.org/10.3390/cryst15110951 - 3 Nov 2025

Viewed by 681

Abstract

Thermoelectric materials enable the direct conversion of heat into electricity, but progress is often limited by challenges in reproducibility and stability. Bi₂O₂Se has recently attracted attention as a promising candidate; however, reported transport properties of undoped polycrystalline samples vary [...] Read more.

Thermoelectric materials enable the direct conversion of heat into electricity, but progress is often limited by challenges in reproducibility and stability. Bi₂O₂Se has recently attracted attention as a promising candidate; however, reported transport properties of undoped polycrystalline samples vary by several orders of magnitude, complicating its use as a baseline for doping studies. In this work, we investigate the sources of variability and identify key factors including precursor contamination, reactions with quartz ampoules and graphite dies, grain size effects, and surface oxidation. To mitigate these issues, we employed calcination of Bi₂O₃ precursors, synthesis with controlled temperature gradients, coarse-fraction powders, and hot pressing in Si₃N₄ dies. The resulting polycrystalline Bi₂O₂Se exhibits improved reproducibility, reduced sensitivity to thermal cycling, and characteristic transport values around σ_RT ≈ 500 S·m⁻¹ and S ≈ −300 μV·K⁻¹ at room temperature. This is a good starting point for further doping studies and a prerequisite of thermoelectric efficiency studies in the future, which can reveal the true thermoelectric potential of this material. Full article

(This article belongs to the Special Issue Research Progress on Thermoelectric Materials)

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18 pages, 8734 KB

Open AccessEditor’s ChoiceArticle

Effect of Current Density on Shear Performance and Fracture Behavior of Cu/Sn-58Bi/Cu Solder Joints

by Kailin Pan, Zimeng Chen, Menghao Liu, Zhanglong Ke, Bo Wang, Kaixuan He, Wei Huang and Siliang He

Crystals 2025, 15(11), 945; https://doi.org/10.3390/cryst15110945 - 31 Oct 2025

Viewed by 678

Abstract

Characterized by its low melting temperature of 138 °C, the eutectic Sn-58Bi solder expands the melting temperature range of interconnect joints in electronic packaging, making it widely used in multi-level packaging processes. However, its reliability at higher current densities poses a challenge. This [...] Read more.

Characterized by its low melting temperature of 138 °C, the eutectic Sn-58Bi solder expands the melting temperature range of interconnect joints in electronic packaging, making it widely used in multi-level packaging processes. However, its reliability at higher current densities poses a challenge. This paper employs a hybrid process combining laser soldering and hot-air reflow to fabricate Cu/Sn-58Bi/Cu solder joints in ball grid array (BGA) structures. Through mechanical testing under current loading, the effects of increasing current density (0 A/cm², 0.85 × 10³ A/cm², 1.70 × 10³ A/cm², 2.55 × 10³ A/cm², 3.40 × 10³ A/cm², 4.25 × 10³ A/cm²) were studied systematically. Results indicate that the shear strength decreases markedly with increasing current density, exhibiting a reduction of approximately 5.63% to 95.75%. This degradation is initiated by the overall temperature increase and material softening due to Joule heating. It is further exacerbated by the loss of the non-thermal electron wind’s strengthening contribution, which weakens as the dominant thermal impact escalates with current density. Fracture mode transitions from ductile failure within the solder matrix to a ductile-brittle mixture at the solder/IMC interface, with the transition initiating at 3.40 × 10³ A/cm². Finite element simulations reveal that current crowding in Sn-rich regions and at the solder/IMC interface induces localized Joule heating and thermomechanical strain, which jointly drive the degradation in shear strength and the shift in fracture path. Full article

(This article belongs to the Special Issue Recent Research on Electronic Materials and Packaging Technology)

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13 pages, 12024 KB

Open AccessEditor’s ChoiceArticle

Crystal Plasticity Modeling of Mechanical Anisotropy for TiAl Alloy Under Uniaxial and Biaxial Loading

by Wenya Peng, Chunling Zhao, Kun Leng, Kanghe Jiang, Weihua Meng, Bin Ding, Qinghu Meng and Wencheng Liu

Crystals 2025, 15(11), 943; https://doi.org/10.3390/cryst15110943 - 31 Oct 2025

Viewed by 482

Abstract

TiAl alloys are widely used in aerospace applications due to their low density and good mechanical properties. However, their pronounced mechanical anisotropy resulting from the preferred orientations of lamellar crystals remains an important issue. This study investigates the plastic anisotropy of TiAl alloys [...] Read more.

TiAl alloys are widely used in aerospace applications due to their low density and good mechanical properties. However, their pronounced mechanical anisotropy resulting from the preferred orientations of lamellar crystals remains an important issue. This study investigates the plastic anisotropy of TiAl alloys under various stress states using full-field crystal plasticity modeling based on electron backscatter diffraction data. The crystal plasticity simulations successfully reproduce the experimental mechanical anisotropy in uniaxial and biaxial tests. The research combines crystal plasticity simulations with Yld2004-18p anisotropic yield function to develop a predictive model that accurately characterizes the anisotropic yielding behavior of the TiAl alloys under various stress states. The findings demonstrate that the Yld2004-18p anisotropic yield function effectively describes the macroscopic anisotropic response obtained from crystal plasticity simulations, providing an important theoretical foundation for predicting the anisotropic behavior of TiAl alloys in engineering structures. Full article

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16 pages, 3646 KB

Open AccessEditor’s ChoiceArticle

Sintering of Alumina-Reinforced Ceramics Using Low-Temperature Sintering Additive

by Yuriy Alexandrovich Garanin, Rafael Iosifovich Shakirzyanov and Malik Erlanovich Kaliyekperov

Crystals 2025, 15(11), 949; https://doi.org/10.3390/cryst15110949 - 31 Oct 2025

Viewed by 1411

Abstract

Reinforced alumina ceramics are renowned for their high hardness and strength among common oxide ceramics. However, high-temperature or high-pressure treatment is necessary for maximizing values of strength and hardness. In this paper, liquid-phase-assisted pressureless sintering of alumina reinforced with zirconia was studied. Sintering [...] Read more.

Reinforced alumina ceramics are renowned for their high hardness and strength among common oxide ceramics. However, high-temperature or high-pressure treatment is necessary for maximizing values of strength and hardness. In this paper, liquid-phase-assisted pressureless sintering of alumina reinforced with zirconia was studied. Sintering of dense ceramic bodies in relatively low temperatures (up to 1100 °C) was possible with the usage of CuO-TiO₂-Nb₂O₅-based additive, together with an intense milling process. By using the XRD method, the formation of dominant α-Al₂O₃ and m-ZrO₂ phases with small concentrations of secondary ones in experimental samples was confirmed. SEM studies showed that uniform distribution of components in the composite was achieved in samples sintered from intensively milled powders. The significant increase in the values of Vickers hardness and biaxial flexural strength (by 2.6 times) in samples from intensively milled powders at a sintering temperature of 1050 °C was explained by reduced porosity, improved grain distribution, and the formation of the t-ZrO₂ phase in the alumina-reinforced composite. The study clearly showed high potential of the proposed low-temperature sintering method for zirconia-toughened aluminum oxide, which can be used in manufacturing of advanced ceramics. Full article

(This article belongs to the Special Issue Ceramic Materials: Structural, Mechanical and Dielectric Properties)

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20 pages, 21900 KB

Open AccessEditor’s ChoiceArticle

Evolution of the Structural and Phase Composition of Ni–Ti–Cu Alloy Produced via Spark Plasma Sintering After Aging

by Danagul Aubakirova, Elfira Sagymbekova, Yernat Kozhakhmetov, Yerkhat Dauletkhanov, Azamat Urkunbay, Dias Yerbolat, Piotr Kowalewski and Yerkezhan Tabiyeva

Crystals 2025, 15(11), 939; https://doi.org/10.3390/cryst15110939 - 30 Oct 2025

Cited by 2 | Viewed by 709

Abstract

This study investigates the control of the phase-structural state in Ni–45Ti–xCu (x = 5, 7 at.%) shape memory alloys fabricated via a shortened powder metallurgy route: mechanical activation → spark plasma sintering (SPS) → heat treatment. Compact samples were produced from mechanically alloyed [...] Read more.

This study investigates the control of the phase-structural state in Ni–45Ti–xCu (x = 5, 7 at.%) shape memory alloys fabricated via a shortened powder metallurgy route: mechanical activation → spark plasma sintering (SPS) → heat treatment. Compact samples were produced from mechanically alloyed powders (650–750 rpm, up to 5 h) and sintered at 900 °C. The structure and microstructure were characterized using X-ray diffraction (to identify B2/B19′/Ni₄Ti₃ phases and assess ordering) and SEM–BSE/EDS (to analyze morphology, porosity, and Ni-rich precipitates). Two post-processing treatments were applied: single-stage annealing (500 °C, 2 h) and a three-stage treatment (900 °C/30 min → water quenching → 300 °C/20 min). Mechanical alloying transformed the initial elemental powder mixture (fcc-Ni, hcp-Ti, fcc-Cu) into a supersaturated fcc-(Ni, Cu, Ti) solid solution with emerging NiTi phases, with a minimum particle size achieved after ~300 min at 750 rpm. SPS compaction yielded a high-density matrix consisting predominantly of the B2 phase. Single-stage annealing preserved B19′ martensite and Ni₄Ti₃ precipitates, particularly in the 5 at.% Cu alloy. In contrast, the three-stage treatment dissolved the Ni₄Ti₃ precipitates, suppressed the formation of B19′ and R phases, and stabilized a highly ordered B2 matrix. Increasing the Cu content from 5 to 7 at.% significantly enhanced the B2 phase fraction, reduced secondary nickel-rich phases, and improved structural homogeneity, evidenced by a continuous neck network and closed porosity. The optimized condition—7 at.% Cu combined with the three-stage annealing—produced a microstructure with >95% B2 phase, <1% Ni₄Ti₃, and ~98% relative density. This forms the prerequisite microstructural state for a narrow transformation hysteresis and high functional cyclic stability. Full article

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

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25 pages, 12718 KB

Open AccessEditor’s ChoiceArticle

Temperature-Dependent Effectiveness of Ti, Nb, Zr, and Y in Controlling Grain Growth of AISI 304 Austenitic Stainless Steel

by Jaka Burja, Samo Tome and Aleš Nagode

Crystals 2025, 15(11), 931; https://doi.org/10.3390/cryst15110931 - 29 Oct 2025

Viewed by 481

Abstract

Crystal grain size control in steel is critical for achieving mechanical properties. This study investigates the effectiveness of microalloying with titanium, niobium, zirconium, and yttrium to inhibit grain growth with the pinning effect. The comparison of selected microalloying elements in the exact same [...] Read more.

Crystal grain size control in steel is critical for achieving mechanical properties. This study investigates the effectiveness of microalloying with titanium, niobium, zirconium, and yttrium to inhibit grain growth with the pinning effect. The comparison of selected microalloying elements in the exact same conditions is crucial for understanding their effect and is novel. Hot-rolled samples were annealed across a wide range of temperatures (1050 to 1200 °C) for up to eight hours. Microstructural analysis confirmed the presence of stable precipitates and non-metallic inclusions such as Nb(C,N), Ti(C,N), ZrO₂, and Y₂O₃ acting as obstacles to grain boundary migration. All microalloying elements significantly outperformed the reference steel, but their effectiveness was highly dependent on the annealing temperature. Titanium was the most effective inhibitor at lower temperatures (1050 °C), while zirconium maintained control up to 1150 °C. Critically, at the highest temperature of 1200 °C, only the yttrium-alloyed steel retained a fine-grain structure, demonstrating superior thermal stability. Niobium, conversely, only showed a minimal effect at 1050 °C, though this grade also exhibited the highest hardness (up to 165 HB) due to precipitation hardening. The kinetics of grain growth were successfully modeled using the Arrhenius-type Sellars–Whiteman equation, accurately describing the behavior for up to four hours of annealing. The findings provide critical insight for selecting optimal microalloying strategies based on maximum operating temperature. Full article

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

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32 pages, 1868 KB

Open AccessEditor’s ChoiceReview

A Comprehensive Review of Machine-Learning Approaches for Crystal Structure/Property Prediction

by Mostafa Sadeghian, Arvydas Palevicius and Giedrius Janusas

Crystals 2025, 15(11), 925; https://doi.org/10.3390/cryst15110925 - 28 Oct 2025

Cited by 4 | Viewed by 4465

Abstract

Crystal Property Prediction (CPP) and Crystal Structure Prediction (CSP) play an important role in accelerating the design and discovery of advanced materials across various scientific disciplines. Traditional computational approaches to CSP/CPP often face challenges such as high computational costs, limited scalability, and difficulties [...] Read more.

Crystal Property Prediction (CPP) and Crystal Structure Prediction (CSP) play an important role in accelerating the design and discovery of advanced materials across various scientific disciplines. Traditional computational approaches to CSP/CPP often face challenges such as high computational costs, limited scalability, and difficulties in exploring complex energy surfaces. In recent years, the combination of machine learning (ML) has emerged as a powerful approach to overcome these limitations, offering data-driven methods that enhance prediction accuracy while significantly reducing computational expenses. This review provides a comprehensive overview of the evolution of CSP and CPP methodologies, with particular emphasis on the transition from classical optimization algorithms to modern ML-based methods. Various supervised and unsupervised ML algorithms applied in this field are discussed in detail. Beyond structure and property prediction, recent advancements in ML-based modeling of crystal defects are also reviewed. Moreover, several recent case studies on CSP/CPP are presented to demonstrate the practical effectiveness of ML approaches. Finally, the review discusses current challenges and provides recommendations for future research in ML-based investigations of CSP/CPP. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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24 pages, 10390 KB

Open AccessEditor’s ChoiceArticle

Electronic Structure and Binding Characteristics of Ionic Liquid Ions on Li-Metal Surfaces Through a DFT Approach

by Luis A. Selis, Dinau Velazco-Lorenzo, Juan Quillas and Diego E. Galvez-Aranda

Crystals 2025, 15(11), 928; https://doi.org/10.3390/cryst15110928 - 28 Oct 2025

Cited by 1 | Viewed by 1204

Abstract

Understanding the interactions between ionic liquid ions and lithium-metal surfaces is critical for designing safer and more efficient lithium metal batteries. In this work, we use density functional theory to investigate the electronic structure, binding energies, work-function shifts and interfacial charge redistribution of [...] Read more.

Understanding the interactions between ionic liquid ions and lithium-metal surfaces is critical for designing safer and more efficient lithium metal batteries. In this work, we use density functional theory to investigate the electronic structure, binding energies, work-function shifts and interfacial charge redistribution of several ionic liquid ions, including FSI⁻, TFSI⁻,

{P F}_{6}^{-}

,

{B F}_{4}^{-}

, DFOB⁻, Pyr14⁺, and EMIM⁺, on a Li-metal anode (Li_m). Absorption orientation-dependent effects are examined for each molecule. Specifically, differences in charge density and electron localization function analyses revealed unique patterns of electron accumulation and delocalization that highlighted specific atomic roles in interfacial bonding. Interfacial charge transfer is analyzed through Bader charges, revealing a moderate charge redistribution for the cations (EMIM⁺, Pyr14⁺), and a more significant charge uptake for the reactive anions (FSI⁻, TFSI⁻, DFOB⁻). Among cations, EMIM⁺ was determined to have the most interfacial stability, while Pyr14⁺ displayed mid-level reactivity. For the anions, varying tendencies for bond formation with lithium metal and potential fragmentation could be determined. Overall, these discoveries detail an atomistic analysis of ionic liquid to Li_m interactions providing additional pathways for molecular design techniques to stabilize electrolytes performing not high-cost computational calculations. Full article

(This article belongs to the Special Issue Analysis of Halogen and Other σ-Hole Bonds in Crystals (2nd Edition))

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36 pages, 6154 KB

Open AccessEditor’s ChoiceReview

Mechanism and Air Cathode Materials of Photo-Assisted Zinc–Air Batteries for Photoelectrochemical Energy Storage

by Mengmeng Zhang, Haoxiang Wang, Yuanyuan Li and Xiangyu Liang

Crystals 2025, 15(11), 923; https://doi.org/10.3390/cryst15110923 - 27 Oct 2025

Viewed by 950

Abstract

The photo-assisted strategy is an effective technology that combines both photo and electrical energy conversion/storage, which represents the direction of the next generation of green energy utilization technologies. In particular, photo-assisted zinc–air batteries (PAZABs) are novel and innovative devices with the advantages of [...] Read more.

The photo-assisted strategy is an effective technology that combines both photo and electrical energy conversion/storage, which represents the direction of the next generation of green energy utilization technologies. In particular, photo-assisted zinc–air batteries (PAZABs) are novel and innovative devices with the advantages of high efficiency and environmental friendliness. Thanks to the generation and effective separation of photo-generated carriers in photo-response air cathode catalysts, PAZABs possess significantly accelerated kinetics of oxygen reduction reaction and oxygen evolution reaction. Moreover, as a popular kind of newly developed two-electrode photoelectrochemical energy storage device, which could realize direct solar-to-electrochemical energy storage, PAZABs alleviate the limitations of the intermittent nature of solar energy in practical applications. In this study, the working mechanism of photoelectrochemical energy storage devices and PAZABs are thoroughly and systematically introduced; additionally, the design principles and types of photo-response electrode materials are reviewed. Interface engineering has been proven to be an effective strategy to improve the performance of the photo-response air cathode catalysts in PAZABs. Thus, the crucial role of the modulated interface chemistry of heterostructure air cathode catalysts is also summarized. Subsequently, the recent progress in the development of single-atom catalysts is outlined. Finally, this review presents several potential strategies for overcoming bottlenecks in the practical application of PAZABs. Full article

(This article belongs to the Special Issue Materials for Applications in Water Splitting and Battery)

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27 pages, 3329 KB

Open AccessEditor’s ChoiceReview

Bending Fatigue in Additively Manufactured Metals: A Review of Current Research and Future Directions

by Md Bahar Uddin, Sriram Praneeth Isanaka and Frank Liou

Crystals 2025, 15(11), 920; https://doi.org/10.3390/cryst15110920 - 25 Oct 2025

Viewed by 1940

Abstract

Metal additive manufacturing (MAM), also referred to as 3D printing, has proven remarkable in the fabrication of complex metal components in multiple sectors. However, the assessment of this revolutionary process through bending fatigue is frequently impeded due to concerns about mechanical and physical [...] Read more.

Metal additive manufacturing (MAM), also referred to as 3D printing, has proven remarkable in the fabrication of complex metal components in multiple sectors. However, the assessment of this revolutionary process through bending fatigue is frequently impeded due to concerns about mechanical and physical conditions of the printed components. The unique layer-by-layer production process results in varied microstructures, anisotropy, and intrinsic defects that considerably differ from traditionally manufactured wrought metals. This review article aims to integrate and evaluate historical and contemporary research on the bending fatigue of additively manufactured materials. More specifically, the impact of process parameters, build orientation, surface conditions, and post-processing techniques such as machining, surface treatments, and polishing on bending fatigue performance are summarized. Adopting prediction methodologies is emphasized to facilitate flaw detection and thereby ensuring the safe and reliable deployment of AM parts in dynamic load carrying applications. Some future research directions are proposed, including the (i) the development of standardized specimens and test protocols, (ii) the adaptation to miniaturization to overcome challenges in high throughput fatigue testing, (iii) the application of emerging geometries such as the Krouse specimen for mechanistic investigations, and (iv) the possibility of developing a correlation across different testing methods and materials to reduce experimental burden. By synthesizing the recent progresses and identifying unresolved challenges, this review outlines an organized and clear pathway towards future research for the deployment of advanced bending fatigue characterization in AM process. The novel idea of adapting miniaturized Krouse geometries in the bending fatigue testing of additively manufactured metals is a viable prospect for the feasible fabrication of AM fatigue coupons with reduced specimen preparation defects and enhanced fatigue strength. Full article

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

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20 pages, 9089 KB

Open AccessEditor’s ChoiceArticle

Molecular Dynamics Simulation of Oxygen Diffusion in (Pu_xTh_1−x)O₂ Crystals

by Dastan D. Seitov, Kirill A. Nekrasov, Danil A. Ustiuzhanin, Anton S. Boyarchenkov, Yulia A. Kuznetsova, Sergey S. Pitskhelaury and Sanjeev K. Gupta

Crystals 2025, 15(11), 919; https://doi.org/10.3390/cryst15110919 - 25 Oct 2025

Viewed by 654

Abstract

Oxygen diffusion in (Pu_xTh₁_−x)O₂ mixed oxide crystals was investigated using molecular dynamics simulation. The model systems were isolated nanocrystals of 5460 and 15,960 particles, featuring a free surface. The oxygen diffusion coefficient D increased with decreasing [...] Read more.

Oxygen diffusion in (Pu_xTh₁_−x)O₂ mixed oxide crystals was investigated using molecular dynamics simulation. The model systems were isolated nanocrystals of 5460 and 15,960 particles, featuring a free surface. The oxygen diffusion coefficient D increased with decreasing thorium content, in accordance with the decrease in the melting temperature of (Pu_xTh₁_−x)O₂ as x varied from 0 to 1. The temperature dependences D(T) exhibited non-linearity in the Arrhenius coordinates lnD = f(1/kT). The three linear segments of the plots corresponded to the superionic state, a transitional region, and the low-temperature crystalline phase. The transitional region was characterized by maximum values of the effective diffusion activation energy E_D(PuO₂) = 3.47 eV, E_D(ThO₂) = 5.24 eV and a complex collective mechanism of oxygen migration, which involved the displacement of anions into interstitial sites. At lower temperatures, an interstitialcy mechanism of oxygen diffusion was observed. The temperature dependence of D(PuO₂) showed quantitative agreement with low-temperature experimental data. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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14 pages, 22611 KB

Open AccessEditor’s ChoiceArticle

The Strain Evolution and Fracture of GH3535 Alloy Welded Joint Characterized by DIC at Different Temperatures

by Qingchun Zhu, Yucheng Zhu, Jie Wang, Li Jiang and Zhijun Li

Crystals 2025, 15(11), 916; https://doi.org/10.3390/cryst15110916 - 24 Oct 2025

Cited by 1 | Viewed by 513

Abstract

Welding is widely employed in manufacturing processes, with the mechanical properties of welded joints being a primary focus of welding technology research. However, distinct regions of welded joints—including the base metal (BM), heat-affected zone (HAZ), and deposited metal (DM)—exhibit divergent deformation behaviors, which [...] Read more.

Welding is widely employed in manufacturing processes, with the mechanical properties of welded joints being a primary focus of welding technology research. However, distinct regions of welded joints—including the base metal (BM), heat-affected zone (HAZ), and deposited metal (DM)—exhibit divergent deformation behaviors, which collectively influence the fracture behavior of the joints. In this study, the specific locations of strain concentration and fracture in GH3535 alloy welded joints (fabricated using ERNiMo-2 welding wire) were investigated during tensile tests at room temperature (RT) and 700 °C. Characterizations were performed via digital image correlation (DIC), electron backscatter diffraction (EBSD), and transmission electron microscopy (TEM). Results revealed that during RT tension, strain was concentrated in the deposited metal adjacent to the fusion line (FL) which is 200% higher than BM, where cracks also initiated. At 700 °C, strain was mainly concentrated in the deposited metal, where the maximum strain concentration was approximately three times that in the base metal, and fracture also occurred in this region. It has been confirmed through in-suit observations that during high-temperature deformation, the deposited metal of the GH3535 alloy is more prone to strain concentration and simultaneously exhibits lower plasticity. This study advances the understanding of the deformation behavior of GH3535 alloy welded joints through in-suit observation results, and indicates that strengthening the deposited metal (i.e., the region more prone to strain concentration) is a more effective approach to improve the mechanical properties of such welded joints. Full article

(This article belongs to the Special Issue Microstructure and Mechanical Properties of Alloys and Composites)

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20 pages, 9419 KB

Open AccessEditor’s ChoiceArticle

Role of Internal Cyclic Heat Treatment on Regulating Microstructure and Mechanical Properties of Laser Melting-Deposited Ti₂AlNb Alloy

by Chunyan Zhang, Lulu Li, Yupin Lv, Yukun Pan, Zhenghua Hao and Qianying Guo

Crystals 2025, 15(11), 910; https://doi.org/10.3390/cryst15110910 - 22 Oct 2025

Viewed by 861

Abstract

Laser melting deposition (LMD), one of the novel powder-to-powder welding technologies, has emerged as an ideal method for fabricating lightweight high-temperature Ti₂AlNb alloy. However, the high thermal gradients and heat accumulation during the LMD process typically promote grain growth along the [...] Read more.

Laser melting deposition (LMD), one of the novel powder-to-powder welding technologies, has emerged as an ideal method for fabricating lightweight high-temperature Ti₂AlNb alloy. However, the high thermal gradients and heat accumulation during the LMD process typically promote grain growth along the deposition direction, resulting in coarse columnar grains and high internal residual stress. This study investigates the influence of prolonged aging treatment and internal cyclic heat on the microstructure and mechanical properties of Ti₂AlNb alloys. Both long-term aging and internal cyclic heat induce the columnar-to-equiaxed grain morphology transition. A 48 h aging heat treatment at 750 °C facilitates the formation of a B2 + O dual-phase lamellar structure, leading to a significant improvement in room-temperature strength. Internal cyclic heat effectively reduces the cooling rate, eliminates internal stress, and suppresses the precipitation of the brittle and detrimental α₂ phase. This results in a more homogeneous distribution of O-phase laths, raising the room-temperature tensile strength from 938 MPa to 1215 MPa and achieving a high-temperature strength of 1116 MPa at 650 °C. These improvements demonstrate a synergistic enhancement in both room- and high-temperature strength and ductility, which provides an efficient strategy for in situ regulation of the microstructure and mechanical properties of laser-deposited Ti₂AlNb alloys. Full article

(This article belongs to the Special Issue Fatigue and Fracture of Welded Structures)

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17 pages, 4247 KB

Open AccessEditor’s ChoiceArticle

Behavior of Formaldehyde Adsorption on ZnO [1011] Facets: A DFT Study

by Chao Ma, Jingze Yao, Liqin Ding, Xuefeng Xiao, Weiyin Li, Yujie He and Meng Wang

Crystals 2025, 15(11), 911; https://doi.org/10.3390/cryst15110911 - 22 Oct 2025

Viewed by 821

Abstract

Formaldehyde is a toxic gas commonly found in industrial emissions, and ZnO is widely used for its detection due to its excellent gas-sensing properties. Most studies focus on non-polar or low-index ZnO surfaces, whereas investigations on high-index polar surfaces remain limited. In this [...] Read more.

Formaldehyde is a toxic gas commonly found in industrial emissions, and ZnO is widely used for its detection due to its excellent gas-sensing properties. Most studies focus on non-polar or low-index ZnO surfaces, whereas investigations on high-index polar surfaces remain limited. In this work, density functional theory (DFT) was employed to study CH₂O adsorption on the ZnO [

10 \bar{11}

] surface. By exploring various coverages, adsorption sites, and unit cell dimensions, ten stable configurations were identified. A maximum adsorption energy of −2.19 eV/CH₂O on configuration S1 was obtained, surpassing reported low-index surfaces. Strong adsorption originated from dual unsaturated Zn bonds, which promoted C–C formation between CH₂O molecules and induced synergistic Zn–O bonding. Adsorption further led to sp³-like hybridization and O 2p/Zn 3d orbital interactions, significantly narrowing the band gap. Electron redistribution, as evidenced by charge density analysis, revealed strong electronic modulation. This work clarifies the microscopic mechanism of ZnO high-index surfaces, offering insights for optimizing gas-sensing materials. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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10 pages, 3403 KB

Open AccessEditor’s ChoiceArticle

Microstructural and XRD Investigations on Zn After Plastic Deformation

by Alessandra Ceci, Girolamo Costanza and Maria Elisa Tata

Crystals 2025, 15(10), 908; https://doi.org/10.3390/cryst15100908 - 21 Oct 2025

Viewed by 690

Abstract

This work presents a microstructural analysis and X-ray diffraction (XRD) investigation of the plastic deformation in commercially pure, single-phase hexagonal close-packed (hcp) Zn subjected to rolling and tensile tests up to failure. Samples were examined by optical microscope and XRD; hardness was assessed [...] Read more.

This work presents a microstructural analysis and X-ray diffraction (XRD) investigation of the plastic deformation in commercially pure, single-phase hexagonal close-packed (hcp) Zn subjected to rolling and tensile tests up to failure. Samples were examined by optical microscope and XRD; hardness was assessed by Vickers microhardness. High-resolution diffraction profiles with Kα1/Kα2 deconvolution were used to identify deformation-induced texture and to estimate the dislocation density. Results show that rolling (40% thickness reduction) and tensile test change texture and cause peak shifts and broadening, with corresponding microstructural changes. Microhardness changes from 28–45 HV (annealed) to 30–50 HV after deformation. After rolling, the texture (002) is the most intense reflection and (004) increases without significant angular shifts. Tensile tests induce low-angle shifts of (101) and (004), as well as selective texture changes (appearance of (103) and (110)). The (101) full width at half maximum increases from β(2θ) = 0.115° (annealed) to 0.160° (rolled) and 0.140° (after tensile test), yielding dislocation densities from 2.73 × 10⁶ cm⁻² (annealed) to 3.03 × 10¹¹ cm⁻² (rolled) and 3.38 × 10¹⁰ cm⁻² (after tensile test). Finally, this study quantifies the XRD parameters (full width at half maximum, angular shifts and dislocation density). Plastic deformation of pure Zn leads to significant microstructural changes, including grain refinement, the generation of dislocations, and the formation of new crystallographic orientations, which are then observable in XRD patterns as peak broadening, shifts, and texture development. The severity of these effects depends on the level of deformation. Full article

(This article belongs to the Special Issue Microstructure and Characterization of Crystalline Materials)

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12 pages, 4432 KB

Open AccessEditor’s ChoiceArticle

Preliminary Serial Femtosecond Crystallography Studies of Myoglobin from Equine Skeletal Muscle

by Jaehyun Park, Sehan Park and Ki Hyun Nam

Crystals 2025, 15(10), 905; https://doi.org/10.3390/cryst15100905 - 18 Oct 2025

Cited by 1 | Viewed by 835

Abstract

Myoglobin (Mb), a heme-containing protein, plays crucial roles in storing and transporting oxygen in muscle cells. Various Mb structures have been extensively determined using conventional cryogenic crystallography, providing valuable information for understanding the molecular mechanisms of the protein. However, this approach has limitations [...] Read more.

Myoglobin (Mb), a heme-containing protein, plays crucial roles in storing and transporting oxygen in muscle cells. Various Mb structures have been extensively determined using conventional cryogenic crystallography, providing valuable information for understanding the molecular mechanisms of the protein. However, this approach has limitations attributable to cryogenic temperatures and radiation damage. Serial femtosecond crystallography (SFX) using X-ray free-electron lasers is an emerging technique that enables the determination of biologically relevant room-temperature structures without causing radiation damage. In this study, we assessed the crystallization, collection, and processing of SFX diffraction data of Mb from equine skeletal muscle. Needle- and needle cluster-shaped Mb crystals were obtained using the microbatch method. Fixed-target SFX data collection was performed at the Pohang Accelerator Laboratory X-ray Free Electron Laser, yielding 1389 indexed diffraction patterns. The phase problem was solved by molecular replacement. The preliminary Mb structure determined at 2.3-Å resolution in this study exhibited subtle structural differences in the heme environment compared with previously reported Mb structures determined by SFX. These results both confirm the feasibility of myoglobin SFX experiments and establish a foundation for future time-resolved studies aiming to visualize ligand binding and oxygen transport. Full article

(This article belongs to the Section Biomolecular Crystals)

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15 pages, 1977 KB

Open AccessEditor’s ChoiceArticle

Single-Crystal X-Ray Diffraction Studies of Derivatives of Phenolphthalein (3,3-Bis(4-hydroxyphenyl)isobenzofuran-1(3H)-one)

by Brian A. Chalmers, David B. Cordes, Aidan P. McKay, Iain L. J. Patterson, Russell J. Pearson, Joscelyn H. Sequeira-Shuker, Iain A. Smellie and Nadiia Vladymyrova

Crystals 2025, 15(10), 901; https://doi.org/10.3390/cryst15100901 - 17 Oct 2025

Viewed by 850

Abstract

An investigation of the molecular structure of a series of phenolphthalein derivatives is presented. The X-ray structures of thymolphthalein, 2,5-dimethylphenolphthalein, and 2,6-dimethylphenolphthalein have been determined for the first time. Furthermore, a series of related 3-(4-hydroxy-dialkyl)-3-(4-hydroxyphenyl)isobenzofuran-1(3H)-ones have also been prepared, and X-ray [...] Read more.

An investigation of the molecular structure of a series of phenolphthalein derivatives is presented. The X-ray structures of thymolphthalein, 2,5-dimethylphenolphthalein, and 2,6-dimethylphenolphthalein have been determined for the first time. Furthermore, a series of related 3-(4-hydroxy-dialkyl)-3-(4-hydroxyphenyl)isobenzofuran-1(3H)-ones have also been prepared, and X-ray structures obtained. The present study allows for comparison of the structures of substituted phenolphthalein derivatives, with a particular focus on the effect of different alkyl groups on the structures. Full article

(This article belongs to the Section Organic Crystalline Materials)

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30 pages, 6082 KB

Open AccessEditor’s ChoiceReview

Metal–Organic Framework for Plastic Depolymerization and Upcycling

by Kisung Lee, Sumin Han, Minse Kim, Byoung-su Kim, Jeong-Ann Park, Kwang Suk Lim, Suk-Jin Ha and Hyun-Ouk Kim

Crystals 2025, 15(10), 897; https://doi.org/10.3390/cryst15100897 - 16 Oct 2025

Viewed by 1656

Abstract

Plastics are essential in modern life but accumulate as waste. Mechanical reprocessing reduces material quality, whereas thermochemical routes require harsh conditions and are costly to upgrade. Together, these factors hinder the large-scale recovery of plastics into equivalent materials. Metal–organic frameworks provide a programmable [...] Read more.

Plastics are essential in modern life but accumulate as waste. Mechanical reprocessing reduces material quality, whereas thermochemical routes require harsh conditions and are costly to upgrade. Together, these factors hinder the large-scale recovery of plastics into equivalent materials. Metal–organic frameworks provide a programmable platform where reticular design fixes porosity and positions well-defined Lewis, Brønsted, redox, and photoredox sites that can preconcentrate oligomers and align scissile bonds for activation. These attributes enable complementary pathways spanning hydrolysis, alcoholysis, aminolysis, photo-oxidation, electrocatalysis, and MOF-derived transformations, with adsorption-guided capture-to-catalysis workflows emerging as integrative schemes. In this review, we establish common figures of merit such as space–time yield, monomer selectivity and purity, energy intensity, site-normalized turnover, and solvent or corrosion footprints. These metrics are connected to design rules that involve active-site chemistry and transport through semi-crystalline substrates. We also emphasize durability under hot aqueous, alcoholic, or oxidative conditions as essential for producing polymer-grade products. Full article

(This article belongs to the Section Macromolecular Crystals)

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18 pages, 9611 KB

Open AccessEditor’s ChoiceArticle

Design, Preparation and Synergistic Optimization of Mechanical Properties and Thermal Neutron Shielding Performance of Mg-Dy-Sm-Zr Alloys

by Huabing Lu, Chengzhi Duan, Enci Niu, Xiyu Xu, Jia She, Jun Tan, Wei Zhang and Jianjun Mao

Crystals 2025, 15(10), 894; https://doi.org/10.3390/cryst15100894 - 15 Oct 2025

Viewed by 542

Abstract

Addressing the challenge of synergistically optimizing shielding performance and mechanical properties in nuclear radiation shielding materials, this study designed and prepared as-cast Mg-12Dy-xSm-0.4Zr (x = 1, 2, 3) alloys by incorporating rare earth elements Dy and Sm, which possess high thermal neutron absorption [...] Read more.

Addressing the challenge of synergistically optimizing shielding performance and mechanical properties in nuclear radiation shielding materials, this study designed and prepared as-cast Mg-12Dy-xSm-0.4Zr (x = 1, 2, 3) alloys by incorporating rare earth elements Dy and Sm, which possess high thermal neutron absorption cross-sections. The co-addition of Sm and Dy significantly refined the grains and promoted the precipitation of bone-like Mg₅(Sm,Dy) and Mg₄₁Sm₅ phases along grain boundaries. The alloys exhibited favorable mechanical properties, with ultimate tensile strength (UTS) reaching up to 194.6 MPa and elongation (EL) up to 10.9%. However, higher Sm content led to an increased amount of secondary phases at grain boundaries, resulting in stress concentration and a subsequent decline in both yield strength and elongation. Moreover, the combined addition of Dy and Sm markedly enhanced the thermal neutron shielding performance. Experimental results agreed well with Geant4 simulations, showing that both the neutron shielding rate and linear attenuation coefficient improved with increasing Sm content, demonstrating the positive role of Dy and Sm in neutron absorption. The developed alloy achieves simultaneous improvement in mechanical properties and neutron shielding capacity, providing valuable insights for the development of lightweight “function–structure integrated” radiation shielding materials for applications such as nuclear medicine and aerospace. Full article

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

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11 pages, 5008 KB

Open AccessEditor’s ChoiceArticle

Creation of Modified Aluminum Powders with Increased Reactivity for Energy Systems

by Ayagoz E. Bakkara, Ainur S. Khairullina, Aida B. Artykbayeva, Alua E. Maten, Aizhan O. Nugymanova, Anar O. Zhapekova and Bakhtiyar S. Sadykov

Crystals 2025, 15(10), 888; https://doi.org/10.3390/cryst15100888 - 14 Oct 2025

Viewed by 509

Abstract

Aluminium plays a key role in developing modern energy technologies, from electrical systems to high-energy materials, providing a combination of functionality, economy, and reliability, but the oxide film on its particles reduces the effective reactivity. This work aims to increase the reactivity of [...] Read more.

Aluminium plays a key role in developing modern energy technologies, from electrical systems to high-energy materials, providing a combination of functionality, economy, and reliability, but the oxide film on its particles reduces the effective reactivity. This work aims to increase the reactivity of aluminum powder by mechanochemical treatment using modifiers. The materials used were aluminum powder of the ASD brand and graphite of the GL-1 brand. The experiment subjected aluminum powder to mechanochemical treatment (MCT) with different graphite contents. It was shown that MCT significantly increases active aluminum content in the powder due to partial destruction of the oxide film on its surface. In addition, morphological analyses confirm the destruction of the oxide, the graphite coating, and the appearance of lamellar structures measuring 0–58 µm. Thermal analysis shows that the primary exothermic peak shifts from 662.6 °C to 653.9 °C for Al + 10% graphite, and the heat released increases by 27%, which means lower activation energy and more complete oxidation. However, at 20% graphite, the thermal gain decreases, since carbon shields the metal areas. Thus, the optimal content is 10% graphite: at this ratio, the best thermochemical behavior of the powder is achieved. The data obtained indicate that the MCT of aluminum powder with graphite effectively increases its reactivity. The resulting aluminum powders with modified particle surfaces facilitate the development of new technologies for the creation of various high-energy solid propellant systems. For rocket engines, preference is given to solid rocket propellant (SRP), which is a mixture of substances (components) capable of burning in the absence of air, producing a large amount of gaseous working fluid heated to a high temperature, providing thrust. Full article

(This article belongs to the Section Hybrid and Composite Crystalline Materials)

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22 pages, 4819 KB

Open AccessEditor’s ChoicePerspective

Carbon Nanotube Production Pathways: A Review of Chemical Vapor Deposition and Electrochemical CO₂ Conversion, Such as C2CNT

by Gad Licht and Stuart Licht

Crystals 2025, 15(10), 887; https://doi.org/10.3390/cryst15100887 - 14 Oct 2025

Cited by 2 | Viewed by 2118

Abstract

Graphene Nano-Carbons (GNCs) have a huge potential, but current production methods limit their exploration and use. Many GNCs will be explored here with a focus on CNTs (Carbon NanoTubes) (which have some of the highest strengths of any known material, conductivity, EMF absorptivity, [...] Read more.

Graphene Nano-Carbons (GNCs) have a huge potential, but current production methods limit their exploration and use. Many GNCs will be explored here with a focus on CNTs (Carbon NanoTubes) (which have some of the highest strengths of any known material, conductivity, EMF absorptivity, and many other useful properties. Manufacturing them abundantly, inexpensively, and in eco-friendly ways remains a significant challenge. Two CNT/GNCs production methods are compared and reviewed. Traditional Chemical Vapor Deposition (CVD) production heats organic reactants with metal catalysts to form GNC/CNTs. As of now, the CVD CNT production has been limited by the high-energy costs, costs per weight comparable to precious metals, and a high CO₂-footprint. C2CNT is an electrochemical methodology that overcomes the constraints of CVD, while producing high-quality CNT/GNCs. C2CNT is a molten carbonate CO₂-electrolysis that makes GNCs. The C2CNT process also selectively produces a wider variety of CNTs (including helical, magnetic, and doped) and GNCs with higher product specificity than CVD by fine-tuning electrolysis parameters. The wide variety of CNTs/GNCs that can be produced by each of these methods is reviewed and discussed. The goal of this perspective is to compare GNC production methods. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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15 pages, 3607 KB

Open AccessEditor’s ChoiceArticle

Photo-Responsive Brominated Hydrogen-Bonded Liquid Crystals

by Christian Anders, Tejal Nirgude, Ahmed F. Darweesh and Mohamed Alaasar

Crystals 2025, 15(10), 886; https://doi.org/10.3390/cryst15100886 - 14 Oct 2025

Cited by 1 | Viewed by 476

Abstract

This study reports on the preparation and comprehensive characterisation of new brominated hydrogen-bonded liquid crystalline (HBLC) materials. Two distinct series of supramolecular complexes were prepared by hydrogen-bond formation between 3-bromo-4-pentyloxybenzoic acid as the proton donor and non-fluorinated and fluorinated azopyridines with variable terminal [...] Read more.

This study reports on the preparation and comprehensive characterisation of new brominated hydrogen-bonded liquid crystalline (HBLC) materials. Two distinct series of supramolecular complexes were prepared by hydrogen-bond formation between 3-bromo-4-pentyloxybenzoic acid as the proton donor and non-fluorinated and fluorinated azopyridines with variable terminal chains as proton acceptors. The successful formation of a hydrogen bond was confirmed by FTIR spectroscopy. The impact of alkyl chain length and fluorination on the mesomorphic properties of the HBLCs was systematically investigated. The molecular self-assembly was thoroughly examined using polarised optical microscopy (POM) and differential scanning calorimetry (DSC), revealing the presence of smectic C (SmC), smectic A (SmA), and nematic (N) phases, with thermal stability being highly dependent on the molecular architecture. Notably, the introduction of fluorine atoms significantly influenced the phase transition temperatures and the overall mesophase range. Using bromine as a lateral substituent induces the formation of SmC phases in these HBLCs, a feature absent in their non-brominated analogues. Further structural insights were obtained through X-ray diffraction (XRD) investigations, confirming the nature of the observed LC phases. Additionally, the photo-responsive characteristics of these HBLCs were explored via UV-Vis spectroscopy, demonstrating their ability to undergo reversible photoisomerisation upon light irradiation. These findings underscore the critical role of precise molecular design in tailoring the properties of HBLCs for potential applications such as optical storage devices. Full article

(This article belongs to the Special Issue Thermotropic Liquid Crystals as Novel Functional Materials)

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8 pages, 5847 KB

Open AccessEditor’s ChoiceArticle

On-Demand Photopatterned Twisted Nematics for Generation of Polychromatic Vector Fields

by Edvard Grigoryan, Hayk H. Harutyunyan, Hrayr Hakobyan, Sergey A. Shvetsov, Tetiana Orlova, Mushegh Rafayelyan and Vahram L. Grigoryan

Crystals 2025, 15(10), 877; https://doi.org/10.3390/cryst15100877 - 11 Oct 2025

Viewed by 714

Abstract

A simple and efficient approach to spatially addressed polychromatic modulation of light polarization using a photopatterned nematic liquid crystal film is proposed and investigated. In particular, we demonstrate linear polarization structuring of the broadband probe beam, including the formation of polarization singularities under [...] Read more.

A simple and efficient approach to spatially addressed polychromatic modulation of light polarization using a photopatterned nematic liquid crystal film is proposed and investigated. In particular, we demonstrate linear polarization structuring of the broadband probe beam, including the formation of polarization singularities under the adiabatic propagation of linearly polarized light, which is achieved through in situ, rewritable photoalignment of nematic liquid crystal by a pump beam. This opto-optical control of polarization does not involve dynamic phase modulation and enables spatially resolved polarization patterning of broadband linearly polarized light in real time. Full article

(This article belongs to the Section Liquid Crystals)

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