The compression effects on the thermoelastic and thermodynamic properties of cubic zincblende silicon-tin alloy (SiSn) were explored using a multi-methodological approach, deploying data mining methods, theoretical equation-of-state parameters, and the Quasi-Harmonic Debye Model. We analyze the relative volume, isothermal bulk modulus, thermal expansion coefficient, Debye temperature, sound velocity, and microhardness of the SiSn compound under pressures up to 8 GPa. The study commences with the data mining-based searches for a structural model and continues with an analysis of the pressure dependence of the relative volume using the Vinet equation of state, followed by an investigation of the bulk modulus and other related thermoelastic properties. Moreover, the variation of microhardness with temperature is predicted, demonstrating a patent progressive decline as the temperature rises from 0 to 800 K. The thermodynamic properties of the SiSn compound have been explored using the quasi-harmonic Debye model in temperatures ranging from 0 to 800 K and pressures ranging from 0 to 8 GPa, respectively. In addition to the information not found in the literature and offered by this study, our work also establishes a simplified model that can predict the evolution of microhardness as a function of temperature, firstly for the SiSn compound, and perhaps can extend to group-IV semiconductors.

A systematic first-principles investigation of lead-free CsSnX3 (X = Cl, F) perovskites is presented, focusing on the interplay between structural polymorphism and electronic properties. A diverse set of symmetry-distinct poly-morphs was generated using the SPuDS approach and subsequently examined within density functional theory (DFT). Despite substantial variations in global crystal symmetry and octahedral tilting patterns, the electronic band gaps show only minor differences across the examined phases for a given chemical composition. In contrast, a clear increase in the band gap is observed upon substitution of Cl by F, reflecting the influence of halide chemistry on the electronic structure. Furthermore, the calculated band gaps are highly sensitive to the choice of exchange-correlation functional, exceeding the variations induced by structural polymorphism. Complementary analysis using the Global Instability Index provides additional insight into subtle differences in local bonding distortions among the predicted structures. Overall, the structural diversity and electronic characteristics revealed in this study provide a comprehensive framework for understanding CsSnX3 perovskites and offer practical guidance for their synthesis and further optimization as lead-free halide materials. The combination of structural diversity and composition-tunable band gaps in these CsSnX3 perovskites suggests that they are versatile materials worthy of further investigation for various functional applications.

We investigate the crystal-structure energy landscape, pressure-induced polymorphism, and electronic and vibrational properties of lanthanum fluoride sulfide (LaFS) using a multistage workflow that combines large-scale global optimization and prototype-based data mining with machine-learning-assisted screening and first-principles local optimization and property calculations. Global exploration of the empirical-potential landscape and data mining generated nearly 4 million candidate structures, which were screened by symmetry analysis, structural clustering, and ML-energy ranking to select a subset of the most relevant structures for density functional theory refinement. The experimentally known PbClF-type modification is confirmed as the ambient-pressure ground-state structure and sixteen additional polymorphs are identified. Enthalpy calculations predict a pressure-induced phase transition from the tetragonal PbClF-type phase to the orthorhombic TiNiSi-type phase at approximately 16.3 GPa within GGA-PBE. Electronic band structures and densities of states calculated using the GGA-PBE and HSE06 functionals show that all investigated modifications are semiconductors, with the band-gap magnitude and its direct or indirect character strongly dependent on crystal structure. Statistical analysis of structural parameters and COHP-derived bonding quantities identifies those showing the strongest correlation with the band gap and helps describe how structural and bonding variations are associated with changes in the electronic properties of LaFS. Phonon calculations assess the dynamical stability of the ambient-pressure ground-state phase and selected high-pressure phases over the investigated pressure range. The results establish LaFS as a structurally versatile mixed-anion semiconductor and provide a systematic framework for exploring, understanding, and tuning its structural and electronic properties.

The present contribution aims to study the structural, mechanical, dynamic, electronic, optical, and vibrational properties of the NiThSn half-Heusler compound. We used the density functional theory (DFT) as implemented in the Wien2k software. Our data on the elastic constants indicate that the NiThSn compound is mechanically stable with a small elastic anisotropy. The derived electronic energy band structure reveals that the NiThSn half-Heusler compound exhibits semiconductor properties with small indirect band gap, with energies of similar to 0.325 eV using the TB-mBJ functional and 0.294 eV using the PBE-GGA functional, respectively. Furthermore, we interpreted the optical properties, including both real and imaginary parts of the dielectric function as well as the absorption coefficient in the energy range from 0 to 14 eV. The phonon dispersion curve confirms the presence of dynamical stability of the NiThSn compound, with a band gap of similar to 0.5 THz between the optical and acoustic branches regions. To the authors' knowledge, no data have been found in the literature on the electronic and optical properties of the NiThSn half-Heusler compound.

Compositionally complex transitional metal nitrides are an interesting class of ceramics with superior chemical, thermal, and mechanical stability, with a high potential in ultra-high temperature applications and catalysis. The exceptionality in the properties may partly be explained as a consequence of their high configuration entropy. Although promising candidates, the bulk synthesis of compositionally complex metal (carbo)nitrides remains challenging, often limited by purity and scalability due to significant oxygen contamination from gaseous reactants or nitrogen loss. To offset these disadvantages, the current manuscript proposes an alternative synthesis route for the synthesis of a compositionally complex nitride (V, Nb, Ta, Mo, W)N-x, which deviates from the typical solid-state and sputtering methods by employing an organometallic precursor route and a double ammonolysis process. This is a first attempt to synthesize such ceramics with low oxygen contamination in compositionally complex (carbo)nitrides with a scalable production(.) Using a multidisciplinary approach consisting of theoretical methods and experiments, the current study elucidates the evolution and stability of the precursor at high temperatures under carbon, and thereby obtained ceramics at different temperatures.

This study investigates the prediction and synthesis of non-equimolar entropy-stabilised borides based on the (TaxHfxZrxTixNbx)B-2 structure. Using Density Functional Theory (DFT) calculations combined with Special Quasirandom Structures (SQS), formation energy was applied to identify stable single-phase compositions. Three compositions were selected for experimental study: (Ta0.6Hf0.1Zr0.1Nb0.1Ti0.1)B-2, (Ta0.6Hf0.25Zr0.05Nb0.05Ti0.05)B-2, (Ta0.6Hf0.2Zr0.1Nb0.05Ti0.05)B-2. The effect of different transition metal concentrations on the synthesis and mechanical properties of entropy-stabilised borides was investigated. XRD analysis confirmed the single-phase solid solutions in all cases. These compositions exhibited hardness between similar to 22 and 23 GPa, significantly higher when compared to the equimolar counterpart (similar to 19 GPa). Similarly, the specific wear rate was markedly reduced to 4.03 x 10(-9) mm(3)/Nm, compared to 5.16 x 10(-8) mm(3)/Nm for the equimolar sample. These results demonstrate that refining the high-entropy concept towards non-equimolar, medium-entropy, compositions through precise molar ratio selection enhances mechanical performance in transition metal diborides.

Rare-earth metal (RE), and in particular holmium (Ho) based materials have received considerable attention due to their scientific and industrial applications. While rare-earth metal fluorides and rare-earth metal selenides have been studied for a long time for various applications, as well as their very interesting electronic properties, optical properties, and superconductivity, Holmium selenides and holmium fluoride selenides have only been recently investigated. An exhaustive study of the holmium fluoride selenide (HoFSe) was performed using a multidisciplinary approach, providing fundamental research in this chemical system. Three polymorphs of HoFSe were synthesized through high-temperature experiments and characterized using single-crystal X-ray diffractometry (SCXRD), scanning electron microscopy (SEM), and energy dispersive X-ray (EDX) spectroscopy. Energy landscape exploration and crystal structure prediction (CSP) were performed using global optimization (GO) and data mining (DM) based searches, followed by local optimization using density functional theory (DFT), resulting in alternative crystal structures at non-equilibrium conditions as a function of pressure and temperature. We believe this study provides a unique perspective and complete picture of the structural features of HoFSe which will enable future investigations of properties and applications.

CaZnOS has attracted significant scientific interest, particularly for its layered structure, advanced properties, outstanding doping ability, and structureu2013property relationships. The CaZnOS compound was synthesized through high-temperature experiments and characterized by X-ray powder diffraction (XRPD). The crystal structure of CaZnOS exhibits noncentrosymmetric hexagonal symmetry with the space group P63mc. The spectra of possible CaZnOS polytypes were investigated, predicting structural configurations that differ from those previously proposed or observed in CaZnOS, encompassing bulk crystal forms, nanostructures, or junction-based architectures. All computations were conducted using first-principles density functional theory (DFT) and five different functionals (local density approximation (LDA)u2013Perdewu2013Zunger (PZ), generalized gradient approximation (GGA)u2013Perdewu2013Burkeu2013Ernzerhof (PBE), Becke three-parameter Leeu2013Yangu2013Parr (B3LYP), parameter-free Perdew-Burke-Ernzerhof (PBE0), and Heydu2013Scuseriau2013Ernzerhof (HSE06)). Recently developed algorithms were used for structure prediction, and the predicted CaZnOS polytypes were investigated for their stability and electronic and vibrational properties. Consequently, numerous potential stable and metastable CaZnOS polytypes were identified, opening new possibilities for the synthesis of innovative materials with improved properties.

The defects in zinc oxide crystals are of crucial importance for their usability in many applications and are not yet fully understood. Here, we demonstrate that dioxygen species are present as defects in the grown ZnO, resulting in a bending of the atom layers that lie perpendicular to the c-axis. In the Raman spectra, these defects cause the appearance of bands different from the known bands of perfect ZnO crystals allowed by symmetry. These additional Raman bands, which have been frequently reported for ZnO in the past, can thus be fully explained by the presence of dioxygen species, and the widespread assumption of second-order modes for the assignments of these bands is not necessary. Furthermore, the Raman spectrum belonging to perfect zinc oxide in the ideal wurtzite structure is presented, obtained from small domains in ZnO(0001) crystals exposed to pressures up to 2 GPa. The dependence of the O-O stretching modes on the applied pressure proves the presence of dioxygen species in ZnO, which is also confirmed by phonon calculations of structure models with embedded dioxygen species. The surface quality of the ZnO crystals studied is also reflected in the Raman spectra and is included in the analysis.

Here, we report the hydrothermal synthesis of BFO (bismuth ferrite) and Bi1−xAgxFeO3 (x = 0.01, 0.02) ultrafine nanopowders. The diffraction patterns show that all obtained particles belong to the R3c space group. On top of that, crystal structure prediction has been accomplished using bond valence calculations (BVCs). Several promising perovskite structures have been proposed together with experimentally observed modifications of BFO as a function of silver doping. Magnetization measurements were performed on BFO, both pure and substituted with 1% and 2% of Ag. The addition of Ag in BFO did not affect the Neel temperature, TN = 630 K for all samples; instead, the influence of Ag was observed in the increase in the value and irreversibility of magnetization, which are usual characteristics of weak ferromagnetism. Our calculations based on density functional theory (DFT) are in agreement with the experimental finding of enhanced magnetization upon Ag doping of antiferromagnetic BFO, which is assigned to the perturbation of magnetic-type interactions between Fe atoms by Ag substitutional doping. Additionally, electronic and magnetic properties were studied for all phases predicted by the BVCs study. DFT predicted half-metallicity in the γ phase of BFO, which may be of great interest for further study and potential applications.

Tantalum carbide (TaC) and hafnium carbide (HfC), as well as mixed hafnium tantalum carbides, are of great recent scientific and industrial interest due to their structural features, and thermal, elastic and mechanical properties. In order to identify the possible crystal structure candidates in the Hf0.5Ta0.5C system that are (meta)stable for different pressures, a global search was performed on the energy landscape of the system. The obtained structure candidates were further locally optimized on the DFT level and the relaxed structures were crystallographically analysed and compared. As a result, the experimentally observed rock salt phase was found as a global minimum and dozen additional feasible modifications of Hf0.5Ta0.5C were predicted. Besides the experimentally observed NaCl-type structure, various distorted versions of this structure type were found, as well as modifications exhibiting the NiAs-, ortho- and 5-5-type of structure. Furthermore,mechanical properties including bulk, shear, Young’s moduli, elastic constants and the Vicker hardness were computed for all promising predicted structure candidates. We believe that the present results will help in understanding the structure-property relationship in mixed HfC/TaC systems.

Zinc oxide (ZnO) is a notable semiconductor with a range of interesting electronic and optical properties. Polytypic behavior of crystal structures can strongly affect the properties of materials, especially in ZnO. We report the first prediction of a new 21R polytype in zinc oxide with advanced properties. Ab initio calculations were carried out using two-hybrid functionals: HSE06 and PBE0. Structural properties of different ZnO polytypes were investigated, and theoretical data concurred with experimental results. This can be further exploited for various applications based on their unique properties. Electronic properties were studied using band structures and density of states (DOS). Present DFT calculations agree very well with previous calculations and measurements of known ZnO polytypes, and the new 21R polytype is found as a direct band gap semiconductor. The size of the band gap in the case of the hybrid HSE06 functional is calculated to be 2.79 eV and with PBE0 is 3.42 eV. Understanding the structure-property relationship helps in tailoring ZnO for specific applications and optimizing its performance in various technological contexts, especially as an advanced semiconductor material, with possible applications such as 0D, 1D, 2D, and 3D materials.

Yttrium-dopped hafnia materials have received considerable attention due to their versatile high-temperature applications. Stabilized cubic type of hafnia is highly beneficial for various applications. Its ability to facilitate the movement of oxygen ions through its crystal structure at elevated temperatures makes it suitable for use in oxygen sensors, solid oxide fuel cells, thermal barrier coatings, refractory materials, etc. A multi-disciplinary study has been performed to investigate the yttrium effect on the electronic structure of hafnia using combinations of theoretical and experimental methods. Self-propagation room temperature method (SPRT) was used to synthesize hafnia solid solutions doped with yttrium, followed by microstructural and morphological characterization of the powders. The obtained results were analyzed and discussed using X-ray diffraction (XRD) and field emission electron microscopy (FE SEM). Ellipsometric measurements were conducted in the Ultraviolet-Visible (UV-Vis) spectral range to measure electronic properties. Moreover, the theoretical study of the yttrium-dopped hafnia solid solution with a cubic-type structure was performed using several different computational methods. Crystal structure prediction and electronic properties were computed using Density Functional Theory (DFT) in a combination of several hybrid functionals.

LaFSe and LaFS materials have shown great potential for various optoelectronic applications, such as photovoltaics, light-emitting diodes, and photodetectors. Mixed LaFSe/LaFS compounds have been synthesized through high-temperature experiments. The introduction of sulfur into LaFSe causes distortion in the crystal lattice, leading to changes in the unit cell. A new algorithm is presented that keeps the symmetries of the mixed LaFSe/LaFS phases, and it is combined with ab initio structure optimization in order to efficiently generate and compute models for solid solution-type compounds. There is good agreement between experimental and theoretical data, and additional predicted structures under extreme conditions in various lanthanoid fluoride selenides/sulfides have been introduced. The substitution of selenium for sulfur within the LaFSe lattice can result in some unusual electronic properties, including changes in the size of the band gap, the character of the gap, and the electronic structure of the material.

Hafnium carbide (HfC) is a refractory compound known for its exceptional mechanical, thermal, and electrical properties. This compound has gained significant attention in materials science and engineering due to its high melting point, extreme hardness, and excellent thermal stability. This study presents crystal structure prediction via energy landscape explorations of pristine hafnium carbide supplemented by data mining. Apart from the well-known equilibrium rock salt phase, we predict eight new polymorphs of HfC. The predicted HfC phases appear in the energy landscape with known structure types such as the WC type, NiAs type, 5-5 type, sphalerite (ZnS) type, TlI type, and CsCl type; in addition, we predict two new structure types denoted as ortho_HfC and HfC_polytype, respectively. Moreover, we have investigated the structural characteristics and mechanical properties of hafnium carbide at the DFT level of computation, which opens diverse applications in various technological domains.

The stability of mixed-valence V6O13 at high pressures and high temperatures is studied experimentally in multianvil presses both ex situ and in situ using synchrotron energy-dispersive powder diffraction. V6O13 starts to amorphize and decomposes above 18.5 GPa at room temperature. It transforms to rutile-related V0.92O2 above 500 K in the pressure range up to about 15-17.5 GPa. The crystal structure of this new phase (C12/m1, Z = 4) was determined from laboratory single-crystal and powder X-ray diffraction data measured on single crystals grown at 10 GPa and 1373 K. The characteristic feature is the presence of two zigzag V-V chains. One of them has equidistant V atoms, while the other is with short and long V-V distances. In the average-ordered structure (P2/m, Z = 2), both V-V chains are linear and equidistant. The M2 polymorph of VO2 is considered to be the ordered (though distorted) variant of V0.92O2. The experiments are complemented by density functional theory calculations and global explorations of the energy landscape of V6O13 and V0.92O2 compounds at high pressures using a multimethodological approach to construct and predict feasible structures.

Tantalum carbide (TaC) is an extremely hard, brittle, refractory ceramic material with excellent physical properties, which makes it a desirable material in e. g. aerospace industries. In order to explore the range of feasible modifications of TaC, we have executed a crystal structure prediction study of the TaC chemical system using a multi-methodological approach, via enthalpy landscape explorations of pristine TaC at different pressures, supplemented by data mining searches in the ICSD database. Local structure relaxations have been accomplished by using Density Functional Theory (DFT). The global minimum is found to correspond to the equilibrium rock salt (NaCl) type modification. Additionally, eight new phases of tantalum carbide are predicted to be feasible: the WC-type, the NiAs-type, the 5-5-type, the ZnS-type, the RingTaC-type, the CsCl-type, the OrthoTaC-type, and the TetraTaC-type. Furthermore, the elastic and mechanical properties of the predicted TaC modifications were explored on the DFT level of computation. The promising values of some of the mechanical properties of the proposed tantalum carbide modifications suggest that various scientific, industrial, and technological applications of TaC should be possible.

Ti–45Nb alloy biomechanical compatibility was evaluated by a multidisciplinary approach and improved by extreme condition processing. Ab initio calculations of mechanical properties are in very good agreement with experimental observations.