Crystals

13 pages, 7509 KiB

Open AccessArticle

Study on AC Loss of REBCO Tape Encapsulated with Magnetic Materials

by Wei Chen, Rong Jin, Yang Bai, Fei Chi, Jiaqing Xu, Xinsheng Yang and Yunpeng Zhu

Crystals 2025, 15(5), 407; https://doi.org/10.3390/cryst15050407 (registering DOI) - 26 Apr 2025

REBCO coated conductors have a multi-layer structure, and the outer encapsulation layer is generally made of non-magnetic copper material. This paper proposes a new structure of REBCO tape, which replaces the copper layer with magnetic material to explore its transport loss and magnetization [...] Read more.

REBCO coated conductors have a multi-layer structure, and the outer encapsulation layer is generally made of non-magnetic copper material. This paper proposes a new structure of REBCO tape, which replaces the copper layer with magnetic material to explore its transport loss and magnetization loss. The results indicate that copper-encapsulated REBCO tapes have lower transport losses at low currents, while tapes encapsulated with strong magnetic nickel alloy materials have the highest transport losses. At high transport currents, the transport losses of REBCO tapes encapsulated with different materials are almost equal. At low fields, the magnetization loss of the tape encapsulated with strong magnetic nickel alloy is lower, while the magnetization loss of the tape encapsulated with copper is the highest, due to the magnetic shielding effect of the magnetic material. Under high-field conditions, the difference in magnetization loss between magnetic material-encapsulated tapes and copper-encapsulated tapes decreases. Full article

(This article belongs to the Special Issue Superconductors and Magnetic Materials)

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19 pages, 6524 KiB

Open AccessArticle

Hydrogen-Bonded Ladder Motifs in Naphthalene Dicarboxamides: Influence of Linear vs. Angular Amide Orientation

by Abdulrahman Mohabbat, István Boldog, Takin Haj Hassani Sohi, Nils Reistel, Philipp Seiffert and Christoph Janiak

Crystals 2025, 15(5), 406; https://doi.org/10.3390/cryst15050406 (registering DOI) - 26 Apr 2025

Abstract

The crystal structures of naphthalene dicarboxamides, namely 1,4-naphthalene dicarboxamide (1,4-NDA), 2,6-naphthalene dicarboxamide (2,6-NDA), and 2,7-naphthalene dicarboxamide (2,7-NDA), are presented for the first time, along with an analysis of their supramolecular organization. The compounds, obtained in single-crystalline form via solvothermal crystallization from methanol, are [...] Read more.

The crystal structures of naphthalene dicarboxamides, namely 1,4-naphthalene dicarboxamide (1,4-NDA), 2,6-naphthalene dicarboxamide (2,6-NDA), and 2,7-naphthalene dicarboxamide (2,7-NDA), are presented for the first time, along with an analysis of their supramolecular organization. The compounds, obtained in single-crystalline form via solvothermal crystallization from methanol, are stable in air to near 350 °C and have melting points above 300 °C. In their densely packed structures (ρ = 1.43–1.47 cm³g⁻¹) the combination of

C_{1}^{1}

(4) chains and

R_{2}^{2}

(8) rings generates one-dimensional hydrogen-bonded ladders, with an additional

R_{4}^{2}

(8) pattern. The amide groups and the naphthalene rings form dihedral angles between 22° and 40°. Neighboring H-bond ladders run parallel in 1,4-NDA and 2,6-NDA and are connected by means of the naphthalenedyil cores so that two-dimensional (2D) H-bonded sheets are obtained. Except for a weak intra-sheet π–π stacking in 1,4-NDA, there are no π–π stacking and C–H⋯π interactions. The

R_{2}^{2}

(8) rings act as four-connected nodes, leading to the formation of two-dimensional H-bonded planar sheets with sql topology for the nearly linear dicarboxamides 1,4-NDA and 2,6-NDA and cds topology for the angular 2,7-NDA. Hirshfeld surface analysis and NCI plots provide additional insight into the H-bonding interactions. Full article

(This article belongs to the Section Crystal Engineering)

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14 pages, 2257 KiB

Open AccessArticle

Polyvinyl Alcohol–Polyethylene Glycol Embedded Reduced Graphene Oxide Electronic Nose Sensor for Seafood Monitoring

by Baliram Nadekar, Pravin S. More, Sadaf Jamal Gilani, Yogesh B. Khollam, Ahmad Umar, Abu ul Hassan S. Rana and Marimuthu Palaniswami

Crystals 2025, 15(5), 405; https://doi.org/10.3390/cryst15050405 - 25 Apr 2025

Abstract

This study explores the development of an electronic nose (E-nose) sensor for fish freshness based on a composite of polyvinyl alcohol (PVA), polyethylene glycol (PEG), and reduced graphene oxide (rGO). The sensor leverages the unique properties of the PVA-PEG polymer matrix, such as [...] Read more.

This study explores the development of an electronic nose (E-nose) sensor for fish freshness based on a composite of polyvinyl alcohol (PVA), polyethylene glycol (PEG), and reduced graphene oxide (rGO). The sensor leverages the unique properties of the PVA-PEG polymer matrix, such as its flexibility and moisture responsiveness, in combination with the electrical conductivity of rGO. The PVA-PEG/rGO composite was synthesized through a low-temperature embedding process to ensure the preservation of sensitive biomolecules and prevent thermal degradation. This sensor demonstrates high sensitivity to volatile amines released during fish spoilage, providing real-time food monitoring to maintain freshness. Electrical resistance changes in the rGO network, influenced by the polymer’s interaction with spoilage gases, were correlated with fish freshness levels. The low cost, easy fabrication, and environmentally friendly nature of the PVA-PEG/rGO E-nose sensor make it a promising candidate for use in packaging or direct contact with fish products in the food industry. This study highlights the potential for extending shelf life and reducing food waste through rapid spoilage detection. Full article

(This article belongs to the Special Issue Nanoelectronics and Bioelectronics)

15 pages, 2957 KiB

Open AccessArticle

Evaluating Machine Learning Models for Predicting Hardness of AlCoCrCuFeNi High-Entropy Alloys

by Uma Maheshwera Reddy Paturi, Muhammad Ishtiaq, Pasupuleti Lakshmi Narayana, Anoop Kumar Maurya, Seong-Woo Choi and Nagireddy Gari Subba Reddy

Crystals 2025, 15(5), 404; https://doi.org/10.3390/cryst15050404 - 25 Apr 2025

Abstract

This study evaluates the predictive capabilities of various machine learning (ML) algorithms for estimating the hardness of AlCoCrCuFeNi high-entropy alloys (HEAs) based on their compositional variables. Among the ML methods explored, a backpropagation neural network (BPNN) model with a sigmoid activation function exhibited [...] Read more.

This study evaluates the predictive capabilities of various machine learning (ML) algorithms for estimating the hardness of AlCoCrCuFeNi high-entropy alloys (HEAs) based on their compositional variables. Among the ML methods explored, a backpropagation neural network (BPNN) model with a sigmoid activation function exhibited superior predictive accuracy compared to other algorithms. The BPNN model achieved excellent correlation coefficients (R²) of 99.54% and 96.39% for training (116 datasets) and cross-validation (39 datasets), respectively. Testing of the BPNN model on an independent dataset (14 alloys) further confirmed its high predictive reliability. Additionally, the developed BPNN model facilitated a comprehensive analysis of the individual effects of alloying elements on hardness, providing valuable metallurgical insights. This comparative evaluation highlights the potential of BPNN as an effective predictive tool for material scientists aiming to understand composition–property relationships in HEAs. Full article

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13 pages, 3328 KiB

Open AccessArticle

Effect of Acid Concentration on Structural, Thermal, and Morphological Properties of Cellulose Nanocrystals from Sugarcane Bagasse and Their Reinforcement in Poly(Furfuryl) Alcohol Composites

by Nduduzo L. Khumalo, Samson M. Mohomane, Thembinkosi D. Malevu, Setumo V. Motloung, Lehlohonolo F. Koao and Tshwafo E. Motaung

Crystals 2025, 15(5), 403; https://doi.org/10.3390/cryst15050403 - 25 Apr 2025

Abstract

This study investigates the impact of sulphuric acid concentration (40% vs. 60%) on the extraction of cellulose nanocrystals (CNCs) from alkali-treated sugarcane bagasse (SCB) and their reinforcement in poly(furfuryl) alcohol (PFA) composites. Probing into the physicochemical changes through scanning electron microscopy (SEM) displayed [...] Read more.

This study investigates the impact of sulphuric acid concentration (40% vs. 60%) on the extraction of cellulose nanocrystals (CNCs) from alkali-treated sugarcane bagasse (SCB) and their reinforcement in poly(furfuryl) alcohol (PFA) composites. Probing into the physicochemical changes through scanning electron microscopy (SEM) displayed drastic morphological changes, alkali removal of noncellulosic components followed by sulphuric acid hydrolysis further refined cellulose to nanoscale morphologies. The X-ray diffraction (XRD) study showed that after alkali treatment, the crystallinity was significantly higher (65%), and the crystallinity index of CNCs prepared from 40% H₂SO₄ was greater than the CNCs prepared from 60% H₂SO₄ (61%). Fourier transform infrared spectral and thermogravimetric analysis (TGA) suggested that improving the polymeric performance by the incorporation of a CNC resulted in a decrease in the thermal stability of the modified polyelectrolyte, which was largely attributed to higher sulphate esterification achieved at higher acid concentrations. It is possible to use CNCs to achieve higher mechanical performance while also indicating that optimizing thermal properties and mechanical performance of high-performance materials will require an improved understanding of the microstructural parameters governing the polymer–filler interface. This work demonstrates that acid concentration critically balances CNC crystallinity and thermal performance, offering insights for optimizing sustainable nanocomposites. Full article

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

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17 pages, 5076 KiB

Open AccessArticle

Axinite, a Borosilicate with Extensive Fe-Mn Substitutions at the Scale of Monocrystal Revealed by Micro-XRF Imaging and In Situ Analysis: An Example from the Type Locality at Oisans (France)

by Michel Cathelineau, Olivier Gerbeaud and Chantal Peiffert

Crystals 2025, 15(5), 402; https://doi.org/10.3390/cryst15050402 - 25 Apr 2025

Abstract

Axinite crystals from the type locality (Oisans, French Alps) are considered among the more remarkable specimens known for their quality (lustre, colour, size, and purity) and crystalline forms. However, they have been the subject of only a few in-depth studies. This lack of [...] Read more.

Axinite crystals from the type locality (Oisans, French Alps) are considered among the more remarkable specimens known for their quality (lustre, colour, size, and purity) and crystalline forms. However, they have been the subject of only a few in-depth studies. This lack of knowledge provided the opportunity for a systematic survey of axinites from Saint-Christophe-en-Oisans, where crystals appear to cover an extensive range of Fe-Mn substitution from an Fe-rich (axinite-Fe) to a Mn-rich field (axinite-Mn) in a same crystal, with compositional variations much more significant than initially described. An in-depth characterisation of the chemical zonation of the crystals using EPMA, Raman spectroscopy, X-ray micro-fluorescence, and LA-ICP-MS was carried out on the crystals showing the most significant variability. The micro-XRF method appeared extremely useful for describing spatial variations in chemical composition at the centimetre scale and preparing other in situ methods. Fe(Mg)-Mn substitution covers a large range but the Mn-enriched growth zones are relatively thin and localised at the periphery of crystals. In addition, chemical zonations highlighted in this study also reveal contrasted incorporation of trace elements as a function of the Fe/Mn ratio (in particular, Be, HREE, Sc, Ga, In, and Co), indicating changes in fluid chemistry during the crystal growth. Full article

(This article belongs to the Collection Topic Collection: Mineralogical Crystallography)

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15 pages, 2187 KiB

Open AccessReview

Sustainable Strategies for Wine Colloidal Stability: Innovations in Potassium Bitartrate Crystallization Control

by Yuhan Zhang

Crystals 2025, 15(5), 401; https://doi.org/10.3390/cryst15050401 - 25 Apr 2025

Abstract

Potassium bitartrate (KHT) crystallization, as the dominant factor compromising wine colloidal stability, necessitates advanced control strategies beyond conventional thermodynamic approaches. The formation of tartrate crystals is influenced by various factors, including temperature, pH, and the concentration of tartrate salts. Traditional methods of tartrate [...] Read more.

Potassium bitartrate (KHT) crystallization, as the dominant factor compromising wine colloidal stability, necessitates advanced control strategies beyond conventional thermodynamic approaches. The formation of tartrate crystals is influenced by various factors, including temperature, pH, and the concentration of tartrate salts. Traditional methods of tartrate stabilization, such as cold stabilization and ion-exchange resins, while effective, are associated with high energy consumption and significant environmental impact. In recent years, with the growing emphasis on green and sustainable development, researchers have begun exploring more environmentally friendly innovative technologies. This review examines the factors affecting tartrate crystallization and their implications for wine quality, detailing traditional stabilization techniques as well as newer methods involving protective colloids and stabilizers. Special attention is given to recent advancements in green technologies, such as plasma surface modification, the use of zeolites as wine processing aids, and the synergistic application of algal polysaccharides. Finally, the paper outlines future directions for tartrate stabilization technology, underscoring the importance of green and sustainable practices in the wine industry. Full article

(This article belongs to the Section Liquid Crystals)

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18 pages, 5110 KiB

Open AccessArticle

An Electrochemical Investigation of the Pitting Corrosion of TZM Alloy in Chloride Solution

by Stefan Abbott, Kavindan Balakrishnan, Sean Instasi, Krishnan S. Raja and Indrajit Charit

Crystals 2025, 15(5), 400; https://doi.org/10.3390/cryst15050400 - 24 Apr 2025

Abstract

In this study, cyclic polarization (CP) measurements were conducted on the molybdenum-based titanium–zirconium–molybdenum (TZM) alloy in 3.5% NaCl solutions under varying pH conditions, and the results were compared with those of pure molybdenum. No passivity breakdown was observed during cyclic polarization in acidic [...] Read more.

In this study, cyclic polarization (CP) measurements were conducted on the molybdenum-based titanium–zirconium–molybdenum (TZM) alloy in 3.5% NaCl solutions under varying pH conditions, and the results were compared with those of pure molybdenum. No passivity breakdown was observed during cyclic polarization in acidic and neutral chloride solutions. The surface film formed on the TZM, and pure Mo samples displayed a dual-layered structure, comprising an inner layer of p-type semiconductivity and an outer layer of n-type semiconductivity. The defect density of the n-type layer ranged from 7.5 × 10¹⁷ to 7.5 × 10¹⁹ cm⁻³, while the p-type layer had a carrier density ranging from 2 × 10¹⁸ to 9 × 10¹⁹ cm⁻³. The pure molybdenum samples demonstrated lower passive current densities, lower charge carrier densities, and higher impedance than the TZM alloy. The lower corrosion resistance of TZM alloy could be attributed to the higher dislocation density, which acted as short-circuit paths for Mo diffusion, and the presence of carbides that exhibited a microgalvanic effect. Overall, this study clarified that the localized corrosion reported in the literature was not due to the breakdown of the passive layer but may be linked to the heterogeneous microstructure. Full article

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

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15 pages, 6477 KiB

Open AccessArticle

A Metallurgically Informed Multiscale Integrated Computational Framework for Metal Forming Processes

by Vasilis Loukadakis and Spyros Papaefthymiou

Crystals 2025, 15(5), 399; https://doi.org/10.3390/cryst15050399 - 24 Apr 2025

Abstract

: Predicting the mechanical response of industrial alloys is crucial for optimizing manufacturing processes and improving material performance. Traditional, solely experimental approaches, though effective, are inefficient as they are resource-intensive, requiring extensive laboratory testing and the iterative calibration of processing conditions. These costs [...] Read more.

: Predicting the mechanical response of industrial alloys is crucial for optimizing manufacturing processes and improving material performance. Traditional, solely experimental approaches, though effective, are inefficient as they are resource-intensive, requiring extensive laboratory testing and the iterative calibration of processing conditions. These costs can be avoided through computational/virtual experiments based on a multiscale hierarchical framework that integrates macroscopic approaches, mesoscale modelling as well as atomic level and advanced thermodynamical simulations to study and predict the mechanical response of metallic systems. In the context of this work, a framework for studying the effect of forming on metallic materials is proposed, applied, and validated on the hot extrusion of AA6063. Coupling thermodynamic simulations (including Phase Field) results with literature data establishes a microstructurally accurate representative volume element (RVE) design. This way, the phase fraction and the grain size of the RVE are determined by thermodynamic simulations (ThermoCalc, MICRESS), which can be validated via microstructure characterization. It is known that the mechanical properties of the individual phases affect the macroscopical properties of the material. Using atomic level simulations (i.e., molecular dynamics), the dislocation density of the material is calculated and utilized as an input for a Crystal Plasticity Fast Fourier Transformation simulation. This iterative process can be applied to match all stages of manufacturing processes. The hierarchical and systematic integration of these computational methodologies enables a rigorous analysis of the effect that processing parameters have on the microstructure. This work contributes to the broader effort of creating experiment-free workflows for designing materials and processes by leveraging a multiscale modeling approach. Coupled with experimental data, the predictive accuracy of the mechanical behavior can be further enhanced. Full article

(This article belongs to the Special Issue Innovative Insights into Deformation and Failure of Metallic Alloys)

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22 pages, 10318 KiB

Open AccessArticle

Enhanced Efficiency of Polycrystalline Silicon Solar Cells Using ZnO-Based Nanostructured Layers

by Mihai Oproescu, Adriana-Gabriela Schiopu, Valentin-Marian Calinescu and Janusz D. Fidelus

Crystals 2025, 15(5), 398; https://doi.org/10.3390/cryst15050398 - 24 Apr 2025

Abstract

In the context of the global energy transition, enhancing the efficiency of polycrystalline silicon-based solar cells remains a critical research priority. This study investigates the integration of ZnO-based nanostructured layers. ZnO and Al-doped ZnO nanoparticles, synthesized via hydrothermal methods and concentrated solar power [...] Read more.

In the context of the global energy transition, enhancing the efficiency of polycrystalline silicon-based solar cells remains a critical research priority. This study investigates the integration of ZnO-based nanostructured layers. ZnO and Al-doped ZnO nanoparticles, synthesized via hydrothermal methods and concentrated solar power (CSP) vapor condensation, exhibiting diverse morphologies—nanorods, spheres, and whisker structures—were deposited onto commercial solar cells using the spin coating technique. Structural, morphological, and spectroscopic analyses confirmed the formation of crystalline layers with high active surface areas and controlled morphology. Photovoltaic performance was assessed using a dedicated hardware–software system under real sunlight conditions. The results demonstrate a significant increase in energy efficiency, reaching up to 10.97%, compared with 1.51% for polycrystalline silicon cells without any supplementary layers. This improvement is attributed to enhanced light absorption, reduced carrier recombination, and more efficient charge transport, driven by nanoscale design and doping. This study underscores the importance of sustainable synthesis and morphological control in the development of high-performance and cost-effective solar technologies. Full article

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34 pages, 11868 KiB

Open AccessArticle

Tailoring Al-Doped ZnO Nanoparticles via Scalable High-Energy Ball Milling–Solid-State Reaction: Structural, Optical, and Dielectric Insights for Light-Activated Antimicrobial Defense Against Medical Device Pathogens

by Zurayfah Al-Shammari, Imen Massoudi, Amani Rached, Ibtisam Ababutain, Azzah Alghamdi, Reem Aldakheel, Kamel Adel Amin, Essam Kotb and Amor Ben Ali

Crystals 2025, 15(5), 397; https://doi.org/10.3390/cryst15050397 - 24 Apr 2025

Abstract

This study reports the synthesis of aluminum-doped ZnO nanoparticles (Al-ZnO NPs) via a top-down mechanochemical solid-state reaction (SSR) approach using high-energy ball milling (HEBM) as a rapid, controllable, and efficient method. Al-ZnO samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), [...] Read more.

This study reports the synthesis of aluminum-doped ZnO nanoparticles (Al-ZnO NPs) via a top-down mechanochemical solid-state reaction (SSR) approach using high-energy ball milling (HEBM) as a rapid, controllable, and efficient method. Al-ZnO samples were characterized using X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), and UV-Vis diffuse reflectance spectroscopy. Significantly, the band gap decreased by 0.215 eV when transitioning from pure ZnO to 9 wt.% Al-doped ZnO (Al-ZnO9). TEM analysis showed that after 4 h of milling at 1000 rpm, the particle size was reduced to 59 nm, exhibiting a spherical morphology crucial for enhanced bioactivity. The antimicrobial properties of the Al-ZnO NPs were evaluated using the well diffusion method against various pathogenic microorganisms, with a particular focus on Staph. aureus ATCC 29213 and Staph. epidermidis ATCC 12228, given their clinical significance as common pathogens in infections related to medical implants and prosthetics. Al-ZnO9 demonstrated superior antibacterial performance, producing inhibition zones of 13 mm and 15 mm against Staph. aureus and Staph. epidermidis, respectively. Moreover, exposure to visible light further amplified the antimicrobial activity. This research underscores the potential for the scalable production of Al-ZnO NPs, presenting a promising solution for addressing infections linked to implanted medical devices. Full article

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15 pages, 2935 KiB

Open AccessArticle

Tannic Acid-Loaded Antibacterial Hydroxyapatite-Zirconia Composite for Dental Applications

by Nusrat Yeasmin, Joel Pilli, Julian McWilliams, Sarah Norris and Arjak Bhattacharjee

Crystals 2025, 15(5), 396; https://doi.org/10.3390/cryst15050396 - 24 Apr 2025

Abstract

The development of advanced biomaterials for dental applications has gained significant attention due to the need for enhanced mechanical properties, biocompatibility, and antibacterial activity. Hydroxyapatite (HA) is widely used in bone tissue engineering owing to its chemical similarities to bone. However, biofilm formation [...] Read more.

The development of advanced biomaterials for dental applications has gained significant attention due to the need for enhanced mechanical properties, biocompatibility, and antibacterial activity. Hydroxyapatite (HA) is widely used in bone tissue engineering owing to its chemical similarities to bone. However, biofilm formation and bacterial infection on HA may lead to implant failure and revision surgery. Tannic acid, a polyphenolic compound with strong antibacterial and antioxidant properties, was incorporated into the composite to provide antimicrobial effects, that may address the challenge of biofilm formation on dental surfaces. In this study, the biomedical potential of tannic acid (TA)-loaded hydroxyapatite-zirconia composites were analyzed. The crystallization characteristics, functional groups, and morphology were analyzed using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and field emission scanning electron microscopy (FESEM) analysis. The biocompatibility of composite samples was analyzed through in vitro cell culture studies. The combined effect of TA and zirconia showed antibacterial efficacy against Staphylococcus aureus (S. aureus) after 24 h of sample–bacterial interactions. The results demonstrate that this tannic acid-loaded hydroxyapatite-zirconia composite holds significant promise for improving the performance of dental materials and preventing infections in oral healthcare applications. Full article

(This article belongs to the Special Issue Celebrating the 10th Anniversary of International Crystallography)

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12 pages, 4356 KiB

Open AccessArticle

Unveiling the Impact of 0–20 Gpa Hydrostatic Pressure on the Physical Properties of (Cs₂HfCl₆) Double Perovskite

by Umar Farooq, Nabeel Israr, Belqees Hassan, Ali Alnakhlani, Mohamed Kallel, Wasif ur Rehman and Yong-Long Wang

Crystals 2025, 15(5), 395; https://doi.org/10.3390/cryst15050395 - 24 Apr 2025

Abstract

The current work determines the physical properties of Cs₂HfCl₆ photovoltaic compounds including their structural, electronic, and optical behavior, utilizing the DFT approach. The simulated Cs₂HfCl₆ lattice constants, cell volumes, and bond lengths decrease as the pressure increases [...] Read more.

The current work determines the physical properties of Cs₂HfCl₆ photovoltaic compounds including their structural, electronic, and optical behavior, utilizing the DFT approach. The simulated Cs₂HfCl₆ lattice constants, cell volumes, and bond lengths decrease as the pressure increases from 0 to 20 GPa. The band structure analysis reveals that the calculated under-pressure (0–20 GPa) of Cs₂HfCl₆ is semiconducting with a flexible indirect bandgap (5.44, 2.76, 2.02, 1.45, and 0.99) eV. The electronic bandgap diminishes (0–20 GPa), transitioning the compound from the UV to the visible spectra. This alteration improves the transition from the VBM to the CBM, hence augmenting the optical effectiveness. Concurrently, the dielectric function escalates, enhancing the absorption and conductivity, and causing a red shift in the optical spectra, while diminishing the reflection in the visible spectra. Our findings on the hydraulic pressure (0–20 GPa) and the electrical and optical properties indicate that Cs₂HfCl₆ may be utilized in the development of next-generation solar cells, LEDs, UV sensors, and high-pressure optical instruments. Full article

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17 pages, 22223 KiB

Open AccessArticle

Enhanced Fenton-like Catalytic Activation of Peroxymonosulfate over Macroporous LaFeO₃ for Water Remediation

by Elzhana Encheva, Savina Koleva, Martin Tsvetkov and Maria Milanova

Crystals 2025, 15(5), 394; https://doi.org/10.3390/cryst15050394 - 24 Apr 2025

Abstract

Four different-sized carbon microspheres, CS, obtained by a facile hydrothermal method, are applied as a hard template for the preparation of a series of macroporous LaFeO₃. The average particle size of the CS obtained is between 0.350 and 0.700 µm. The [...] Read more.

Four different-sized carbon microspheres, CS, obtained by a facile hydrothermal method, are applied as a hard template for the preparation of a series of macroporous LaFeO₃. The average particle size of the CS obtained is between 0.350 and 0.700 µm. The macroporous LaFeO₃ are tested in a Fenton-like activation of peroxymonosulfate, PMS, for oxidation of tetracycline hydrochloride, TCH, in model water solution under visible-light irradiation. The effect of parameters such as type of irradiation, temperature of the reaction, and type of the water matrixes was tested. The oxidation of the pollutant TCH is evaluated by total organic carbon and organic nitrogen measurements. The results showed the superior catalytic activity of macroporous LaFeO₃ in comparison to pure LaFeO₃. Rate constants between 0.036 and 0.184 min⁻¹ at 25 °C were obtained. The activation energy for the process with the most active macroporous LaFeO₃ was 33.88 kJ/mol, a value lower than for the catalytic process with PMS only, proving the positive role of the macroporous LaFeO₃ for TCH degradation. Radical scavenger measurements showed that singlet oxygen, produced during the catalytic degradation process, was responsible for the performance of macroporous LaFeO₃/PMS/visible light for TCH degradation. The catalysts proved to be efficient and recyclable. Full article

(This article belongs to the Special Issue Rare Earths-Doped Materials (3rd Edition))

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18 pages, 1358 KiB

Open AccessArticle

Learning Self-Supervised Representations of Powder-Diffraction Patterns

by Shubhayu Das, Markus Vorholt, Andreas Houben and Richard Dronskowski

Crystals 2025, 15(5), 393; https://doi.org/10.3390/cryst15050393 - 23 Apr 2025

Abstract

The potential of machine learning (ML) models for predicting crystallographic symmetry information from single-phase powder X-ray diffraction (XRD) patterns is investigated. Given the scarcity of large, labeled experimental datasets, we train our models using simulated XRD patterns generated from crystallographic databases. A key [...] Read more.

The potential of machine learning (ML) models for predicting crystallographic symmetry information from single-phase powder X-ray diffraction (XRD) patterns is investigated. Given the scarcity of large, labeled experimental datasets, we train our models using simulated XRD patterns generated from crystallographic databases. A key challenge in developing reliable diffraction-based structure-solution tools lies in the limited availability of training data and the presence of natural adversarial examples, which hinder model generalization. To address these issues, we explore multiple training pipelines and testing strategies, including evaluations on experimental XRD data. We introduce a contrastive representation learning approach that significantly outperforms previous supervised learning models in terms of robustness and generalizability, demonstrating improved invariance to experimental effects. These results highlight the potential of self-supervised learning in advancing ML-driven crystallographic analysis. Full article

(This article belongs to the Section Inorganic Crystalline Materials)

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19 pages, 4638 KiB

Open AccessArticle

Structural and Optical Properties of Defected and Exotic Calcium Monochalcogenide Nanoparticles: Insights from DFT and TD-DFT Calculations

by Panagiotis G. Moustris, Alexandros G. Chronis, Fotios I. Michos, Nikos Aravantinos-Zafiris and Mihail M. Sigalas

Crystals 2025, 15(5), 392; https://doi.org/10.3390/cryst15050392 - 23 Apr 2025

Abstract

In this work, the structural and optical properties of calcium monochalcogenide nanoparticles were numerically examined by using Density Functional Theory and Time Dependent Density Functional Theory. The composition of the examined nanoparticles was obtained from an initial cubic-like building block of the form [...] Read more.

In this work, the structural and optical properties of calcium monochalcogenide nanoparticles were numerically examined by using Density Functional Theory and Time Dependent Density Functional Theory. The composition of the examined nanoparticles was obtained from an initial cubic-like building block of the form Ca₄Y₄, where Y could be one of the chalcogen elements sulfur, selenium, and tellurium, after its proper numerical examination to check their structural stability. The examined nanoparticles were then created from these initial cubic-like building blocks after their elongation along one, two, and three perpendicular directions. Τhe Absorption Spectrum, the Binding Energy, together with the highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) gap, were included in the calculations of the studied calcium monochalcogenides. The calculations provided numerical evidence regarding the existence of stable structures for a wide range of morphologies. In addition, the examination of the properties of such nanostructures after placing different kinds of defects was also included in the calculations, thus leading to new groups of nanoparticles with several potential uses in technological applications, such as hydrogen storage, CO₂ capture, and ultraviolet-responsive devices. Full article

(This article belongs to the Special Issue Celebrating the 10th Anniversary of International Crystallography)

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14 pages, 2801 KiB

Open AccessArticle

Single Crystal Growth and Structural Study of the New MCu₂Zn₂₀ (M = Nb, Hf) Compounds

by Sarah M. Longworth, Marium M. Mou, Nusrat Yasmin, Md Fahel Bin Noor, Ridwan Sakidja and Tiglet Besara

Crystals 2025, 15(5), 391; https://doi.org/10.3390/cryst15050391 - 23 Apr 2025

Abstract

Two new cage-structured compounds—NbCu₂Zn₂₀ and HfCu₂Zn₂₀—belonging to the MM’₂X₂₀ (M, M’ = transition or rare earth metals, and X = Al, Zn, or Cd) family of structures have been synthesized via [...] Read more.

Two new cage-structured compounds—NbCu₂Zn₂₀ and HfCu₂Zn₂₀—belonging to the MM’₂X₂₀ (M, M’ = transition or rare earth metals, and X = Al, Zn, or Cd) family of structures have been synthesized via the self-flux method. The new compounds crystallize in the space group

F d \bar{3} m

with lattice parameter 13.9013(2) Å for NbCu₂Zn₂₀ and 13.9856(2) Å for HfCu₂Zn₂₀. The structures follow the expected metallic radii trend in MM’₂₀Zn₂₀ (M = Nb or Hf, M’ = Mn, Fe, Co, Ni, and Cu). While NbCu₂Zn₂₀ is stoichiometric, HfCu₂Zn₂₀ exhibits Cu/Zn site mixing and Hf-site underoccupancy, resulting in a final stoichiometry of Hf_0.96Cu_1.67Zn_20.33 (Hf_1–δCu_2–_xZn₂₀₊_x, δ = 0.04, x = 0.33). Full article

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20 pages, 2884 KiB

Open AccessArticle

A Data-Driven Framework for Accelerated Modeling of Stacking Fault Energy from Density of States Spectra

by Md Tohidul Islam and Scott R. Broderick

Crystals 2025, 15(5), 390; https://doi.org/10.3390/cryst15050390 - 23 Apr 2025

Abstract

Stacking fault energy (SFE) is a critical property governing deformation mechanisms and influencing the mechanical behavior of materials. This work presents a unified framework for understanding and predicting SFE based solely on an electronic structure representation. By integrating density of states (DOS) spectral [...] Read more.

Stacking fault energy (SFE) is a critical property governing deformation mechanisms and influencing the mechanical behavior of materials. This work presents a unified framework for understanding and predicting SFE based solely on an electronic structure representation. By integrating density of states (DOS) spectral data, dimensionality reduction techniques, and machine learning models, it was found that the SFE behavior is indeed represented within the electronic structure and that this information can be used to accelerate the prediction of SFE. In the first part of this study, we established quantitative relationships between electronic structure and microstructural features, linking chemistry to mechanical properties. Using principal component analysis (PCA) and uniform manifold approximation and projection (UMAP), we identified key features from high-resolution vector representation of DOS data and explored their correlation with SFE. The second part of this work focuses on the predictive modeling of SFE, where a machine learning model trained on UMAP-reduced features achieved high accuracy (R² = 0.86, MAE = 15.46 mJ/m²). To bridge length scales, we extended this methodology to predict SFE in alloy systems, leveraging single-element data to inform multi-element alloy design. We illustrate this approach with Cu-Zn alloys, where the framework enabled rapid screening of compositional space while capturing complex electronic structure interactions. The proposed framework accelerates alloy design by reducing reliance on costly experiments and ab initio calculations. Full article

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26 pages, 5096 KiB

Open AccessArticle

Chromone-Based Copper(II) Complexes as Potential Antitumour Agents: Synthesis, Chemical Characterisation and In Vitro Biological Evaluation

by Nikolina Filipović, Tomislav Balić, Martina Medvidović-Kosanović, Dominik Goman, Berislav Marković, Dalibor Tatar, Sunčica Roca and Katarina Mišković Špoljarić

Crystals 2025, 15(5), 389; https://doi.org/10.3390/cryst15050389 - 23 Apr 2025

Abstract

Three new complexes of copper(II) and chromone-2-carboxylic acid, a ligand from the group of hydroxypyrones, were synthesised according to the principles of green chemistry. The complexes were characterised by FT–IR and NMR spectroscopy, thermal and electrochemical analysis, and their structures are proposed. The [...] Read more.

Three new complexes of copper(II) and chromone-2-carboxylic acid, a ligand from the group of hydroxypyrones, were synthesised according to the principles of green chemistry. The complexes were characterised by FT–IR and NMR spectroscopy, thermal and electrochemical analysis, and their structures are proposed. The results show the formation of mononuclear (1) and dinuclear hydroxo-bridged dinuclear copper(II) complexes (2 and 3). The results of cyclic voltammetry show that the copper in all complexes is in the +2-oxidation state. The antiproliferative activity was determined by MTT assay on 2D cell models in vitro on seven cell lines. The activity spectrum of complexes 1–3 ranged from the highest to the lowest value in the tumour cell lines tested, in the following order: Hep G2 > NCI-H358 > HT-29 > KATO III > MDA-MB 231 > Caco-2. The most effective concentration was 10⁻⁵ mol dm⁻³, which suppressed the growth of Hep G2 cells as follows: 69.5% (1), 64.8% (2) and 64% (3). The calculated selectivity index clearly shows that Hep G2 is the most sensitive cell line to copper complexes (SI = 1.623 (1); 1.557 (2), 1.431 (3). Full article

(This article belongs to the Special Issue Green Approach in Synthesis of Bio-Inspired Materials (Second Edition))

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