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Compositionally complex transitional metal nitrides are possible candidates for ultra-high temperature usage and are known for their superior properties due to the high configuration entropy. It is often difficult to synthesize pure metal nitrides in bulk, due to significant oxygen contamination; hence, they are synthesized mainly as thin films through magnetron sputtering, chemical vapor deposition or surface nitridation of high entropy alloys. The present article reports on a single-phase compositionally complex ceramic, i.e., (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)NxC1−x, that is synthesized for the first time by employing an organometallic precursor route and using a double ammonolysis process. A multidisciplinary approach is performed to study these compositionally complex nitride and carbonitride systems, including experimental and theoretical investigations.

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.

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.

Bismuth ferrite (BFO, BiFeO3), exhibiting both ferromagnetic and ferroelectric properties at room temperature, is one of the most researched multiferroic materials with a growing number of technological applications. In the present study, using a combined theoretical–experimental approach, we have investigated the influence of Ho-doping on the structural, electronic and magnetic properties of BFO. Synthesis and structural XRD characterization of Bi1 xHoxFeO3 (x = 0.02, 0.05, and 0.10) nanopowders have been completed. After structure prediction of Ho-doped BiFeO3 using bond valence calculations (BVC), six most favorable candidates were found: a-, b-, g-, R-, T1, and T2. Furthermore, all structure candidates have been examined for different magnetic ordering using DFT calculations. The magnetic behavior of the synthesized materials was investigated using a SQUID magnetometer equipped with an oven. The plethora of magnetic and electronic properties of the Ho-doped BFO that our theoretical research predicted can open up rich possibilities for further investigation and eventual applications.

Crystalline TiO2 has many practical applications as a photocatalytic material. The structures and relative energies of eleven different modifications of bulk structures with TiO2 composition were theoretically investigated in this study. Calculations were performed by the DFT method with LDA-PZ functional as implemented in CRYSTAL17 code. Structural parameters, energy- volume curves and electronic band gaps were calculated and analyzed. This study aimed to gain insight into the electronic structure of various modifications of crystalline pristine TiO2 and their phase transitions especially applicable at extreme pressure and temperature conditions. The information obtained in this study may contribute to future research on the structure and various properties (electronic, mechanical…) of such systems, as well as their potential application in various scientific fields and advanced technology.

The Cr−Si−N system is of great interest for materials with advanced tribological and mechanical properties. So far, experimental data have been reported on Cr−Si−N coating, nanocrystalline phases, and thin films, together with theoretically predicted 1D and 2D hetero-structures, and 3D bulk Cr2SiN4 modifications. This study predicts possible bulk Cr−Si−N phases with the composition CrSi2N4. A multi-methodological approach has been employed to explore the system's energy landscape, where global optimization was combined with data mining and the Primitive Cell for Atom Exchange (PCAE) method. Local optimization of the structure candidates was performed on the DFT level using the GGA-PBE and the LDA-PZ approximation. The ten energetically most favorable structure candidates discovered in the CrSi2N4 chemical system mostly exhibited monoclinic symmetry but with a variety of structural features, from zeolite-like structures to polytypic behavior. Finally, the bulk modulus of these possible modifications was computed for a pressure range of up to 10 GPa.

Studying the interaction of inorganic systems with organic ones is a highly important avenue for finding new drugs and treatment methods. Tumor cells show an increased demand for amino acids due to their rapid proliferation; thus, targeting their metabolism is becoming a potential oncological therapeutic strategy. One of the inorganic materials that show antitumor properties is titanium dioxide, while its doping was found to enhance interactions with biological systems. Thus, in this study, we investigated the energy landscape of glutamine (L), an amino acid, on pristine and doped TiO2 surfaces. We first locally optimized 2D-slab structures of pristine and Au/Ag/Cu-doped anatase (001 and 101 surfaces) and similarly optimized a single molecule of glutamine in vacuum. Next, we placed the pre-optimized glutamine molecule in various orientations and on a variety of locations onto the relaxed substrate surfaces (in vacuum) and performed ab initio relaxations of the molecule on the substrate slabs. We employed the DFT method with a GGA-PBE functional implemented in the Quantum Espresso code. Comparisons of the optimized conformations and electronic structures of the amino acid in vacuum and on the surfaces yield useful insights into various biological processes.

Calcium carbonate and gypsum are very common and widespread minerals widely used in many fields. However, in order to investigate their behavior under extreme conditions of pressure and temperature, a data-mining ab initio approach has been performed. To analyze structural stability and explore different CaCO3 and gypsum phases in these extreme conditions, the most interesting modifications have been submitted to the DFT calculations. Local optimizations have been performed using the CRYSTAL17 solid-state-quantum-chemical program. Total energies of different gypsum phases are presented and it seems that among the calcite phases, the Calcite I (CaCO3 I) phase has the lowest calculated total energy using the three different functionals in agreement with experimental data. Each of the modified phases of these minerals has been discussed and presented in this study. Due to the very wide industrial and technological application of these natural minerals, further investigation could be of great importance, especially their performances in extreme environments.

Innovative materials used in high-technology applications are called advanced materials. These materials can be completely new or typical traditional materials (e.g., metals, ceramics)whose properties have been enhanced to become advanced. This talk will cover the theoretical investigation of various advanced ceramic materials in connection to the experimental results. The first part will include the basics of modeling and structure prediction of ceramic materials, such as global optimization, quantum mechanics, and supercell method, as well as current developments in the Inorganic Crystal Structure Database (ICSD), theoretical crystal structure data, and data mining.In the next part, theoretical methods will be applied to the specific ceramic compounds. A plethora of state-of-the-art quantum mechanical methods will be presented, including Density-functional theory (DFT),LDA-PZ and GGA-PBE, or hybrid B3LYP and HSE functionals, and a combination of quantum mechanics with data mining and global optimization, as well as the newly developed Primitive Cell approach for Atom Exchange (PCAE) method applied on ZnO/ZnS polytypic (hetero)structures and unknown Cr2SiN4 compounds. Finally, the theoretical modeling of materials properties has been presented. Since many of the investigated materials show a large number of desirable properties for industrial applications,ab initio calculations of electronic, elastic, and mechanical properties will be presented and compared with experiments when available.

Oxynitrides of cerium are expected to have many useful properties but have not been synthesized so far. We identified possible modifications of a not-yet-synthesized Ce3O3N compound, combining global search (GS) and data mining (DM) methods. Employing empirical potentials, structure candidates were obtained via global optimization on the energy landscape of Ce3O3N for different pressure values. Furthermore, additional feasible structure candidates were found using data mining of the ICSD database. The most promising structure candidates obtained were locally optimized at the ab initio level, and their E(V) curves were computed. The structure lowest in total energy, Ce3O3N-DM1, was found via local optimization starting from a data mining candidate and should be thermodynamically metastable up to high pressures.

Multicomponent oxide with pyrochlore structure (A2B2O7), containing 7 different A-site cations and 3 B-site cations in equiatomic amounts, was synthesized. Powders with nominal composition (La1/7Sm1/7Nd1/7Pr1/7Y1/7Gd1/7Yb1/7)2(Sn1/3Hf1/3Zr1/3)2O7 were fabricated through a reaction of metal nitrates (A-site) and metal chlorides (B-site) with sodium hydroxide during the solid state displacement reaction. Room temperature synthesis initially resulted in the obtainment of amorphous powders, which crystallized after subsequent calcination to form single crystalline compounds. Crystalline high-entropy ceramic powders formation took place at temperatures as low as 750 °C. During calcination, defective fluorite (F-A2B2O7) and crystal pyrochlore (Py-A2B2O7) structures coexist. A large number of cations induce the obtainment of stable high-entropy pyrochlores. Results showed that sintering at 1650 °C lead to pure crystalline single-phase pyrochlore formation. High-density ceramic, free of additives, was obtained after powders were compacted and subjected to pressureless sintering at 1650 °C. Multicomponent pyrochlore structure was investigated using the theoretical and experimental multi-methodological approach.

Aluminum nitride (AlN) and boron nitride (BN) are well-known ceramic materials with numerous valuable properties, whereas recently there is a growing field of research on the AlN/BN advanced ceramic materials. Here, we present a study on boron-rich AlN, structural and electronic properties, and structure–property relationship. Several AlxB1−xN solid solutions (x = 1, .875, .75, and .625) have been investigated, and structure optimization has been performed for four different structure types: h-BN, wurtzite, sphalerite, and rock salt. First-principles calculations were performed using hybrid B3LYP functional. New modifications and compounds have been predicted as a function of boron concentration in AlN, and especially, interesting phase transitions were found at extreme pressure conditions. Electronic properties and band structures were computed, and the possibility for bandgap tuning has been discovered. The present study, and especially the structure–property relationship, gives new possibilities for bandgap engineering in boron-rich AlN electroceramic materials.

ZnO/ZnS core/shell nanostructures, which are studied for diverse possible applications, ranging from semiconductors, photovoltaics, and light-emitting diodes (LED), to solar cells, infrared detectors, and thermoelectrics, were synthesized and characterized by XRD, HR-(S)TEM, and analytical TEM (EDX and EELS). Moreover, band-gap measurements of the ZnO/ZnS core/shell nanostructures have been performed using UV/Vis DRS. The experimental results were combined with theoretical modeling of ZnO/ZnS (hetero)structures and band structure calculations for ZnO/ZnS systems, yielding more insights into the properties of the nanoparticles. The ab initio calculations were performed using hybrid PBE0 and HSE06 functionals. The synthesized and characterized ZnO/ZnS core/shell materials show a unique three-phase composition, where the ZnO phase is dominant in the core region and, interestingly, the auxiliary ZnS compound occurs in two phases as wurtzite and sphalerite in the shell region. Moreover, theoretical ab initio calculations show advanced semiconducting properties and possible band-gap tuning in such ZnO/ZnS structures.

High-entropy rare-earth (RE) zirconates with pyrochlore structure were successfully fabricated by pressureless and spark plasma sintering. RE2Zr2O7 compound with nominal composition (La0.2Y0.2Gd0.2Nd0.2Sm0.2)Zr2O7 was prepared by simple glycine nitrate procedure (GNP). GNP process yielded powders with low crystallinity and after subsequent calcination, well crystalline ceramics were formed. During calcination defective fluorite (F-RE2Zr2O7) and crystal pyrochlore (Py-RE2Zr2O7) structures coexist. Formation of pure crystalline pyrochlore occurs after sintering at 1450°C. High-density ceramics, free of any additives, were obtained after powders compaction and pressureless (PS), as well as field assisted sintering technique (FAST) at 1450°C. Theoretical investigations of the high-entropy RE2Zr2O7 pyrochlore systems were performed. Unit cell parameter of the obtained Py-RE2Zr2O7 is 10.5892(2)Å and 10.5999(2)Å for PS and FAST sintering, respectively, which is in good agreement with the results of Density Functional Theory (DFT) calculations. The thermal diffusivity of sintered samples at room temperature was ∼0.7mm2/s for both sintering methods.ResumenSe fabricaron con éxito, mediante sinterización por plasma sin presión y por chispa, los circonatos de tierras raras (RE) de alta entropía con estructura de pirocloro. El compuesto RE2Zr2O7 con composición nominal (La0,2Y0,2Gd0,2Nd0,2Sm0,2)Zr2O7 se preparó mediante un procedimiento simple de nitrato de glicina (GNP). El proceso GNP produjo polvos con baja cristalinidad y después de la posterior calcinación, se formaron cerámicas bien cristalinas. Durante la calcinación coexisten estructuras defectuosas de fluorita (F-RE2Zr2O7) y pirocloro cristalino (Py-RE2Zr2O7). La formación de pirocloro cristalino puro se produce después de la sinterización a 1.450°C. Después de la compactación de polvos y sin presión (PS), así como por la técnica de sinterización asistida en campo (FAST) a 1.450 oC, se obtuvieron cerámicas de alta densi

We report on a new class of ZnO/ZnS nanomaterials based on the wurtzite/sphalerite architecture with improved electronic properties. Semiconducting properties of pristine ZnO and ZnS compounds and mixed ZnO1−xSx nanomaterials have been investigated using ab initio methods. In particular, we present the results of our theoretical investigation on the electronic structure of the ZnO1−xSx (x = 0.20, 0.25, 0.33, 0.50, 0.60, 0.66, and 0.75) nanocrystalline polytypes (2H, 3C, 4H, 5H, 6H, 8H, 9R, 12R, and 15R) calculated using hybrid PBE0 and HSE06 functionals. The main observations are the possibility of alternative polytypic nanomaterials, the effects of structural features of such polytypic nanostructures on semiconducting properties of ZnO/ZnS nanomaterials, the ability to tune the band gap as a function of sulfur content, as well as the influence of the location of sulfur layers in the structure that can dramatically affect electronic properties. Our study opens new fields of ZnO/ZnS band gap engineering on a multi-scale level with possible applications in photovoltaics, light-emitting diodes, laser diodes, heterojunction solar cells, infrared detectors, thermoelectrics, or/and nanostructured ceramics.

Aluminum nitride (AlN) and boron nitride (BN) are well-known ceramic materials with numerous valuable properties, whereas recently there is a growing field of research on the AlN/BN advanced ceramic materials. Here, we present a study on boron-rich AlN, structural and electronic properties, and structure–property relationship. Several AlxB1−xN solid solutions (x = 1,.875,.75, and.625) have been investigated, and structure optimization has been performed for four different structure types: h-BN, wurtzite, sphalerite, and rock salt. First-principles calculations were performed using hybrid B3LYP functional. New modifications and compounds have been predicted as a function of boron concentration in AlN, and especially, interesting phase transitions were found at extreme pressure conditions. Electronic properties and band structures were computed, and the possibility for bandgap tuning has been discovered. The present study, and especially the structure–property relationship, gives new possibilities for bandgap engineering in boron-rich AlN electroceramic materials. © 2022 The American Ceramic Society.

High-entropy rare-earth (RE) zirconates with pyrochlore structure were successfully fabricated by pressureless and spark plasma sintering. RE2Zr2O7 compound with nominal composition (La0.2Y0.2Gd0.2Nd0.2Sm0.2)Zr2O7 was prepared by simple glycine nitrate procedure (GNP). GNP process yielded powders with low crystallinity and after subsequent calcination, well crystalline ceramics were formed. During calcination defective fluorite (F-RE2Zr2O7) and crystal pyrochlore (Py-RE2Zr2O7) structures coexist. Formation of pure crystalline pyrochlore occurs after sintering at 1450 C. High-density ceramics, free of any additives, were obtained after powders compaction and pressureless (PS), as well as Field Assisted Sintering Technique (FAST) at 1450 C. Theoretical investigations of the high-entropy RE2Zr2O7 pyrochlore systems were performed. Unit cell parameter of the obtained Py-RE2Zr2O7 is 10.5892(2) Å and 10.5999(2) Å for PS and FAST sintering, respectively, which is in good agreement with the results of Density Functional Theory (DFT) calculations. The thermal diffusivity of sintered samples at room temperature was ~0.7 mm2 /s for both sintering methods.