The search for efficient photocatalysts for sustainable hydrogen production has driven growing interest in barium titanate (BaTiO3)-based materials, particularly through polymorph control, surface engineering, and nonmetal and transition-metal doping. In this work, we provide an atomic-scale understanding of structural modifications in nitrogen-, fluorine-, and rhodium-doped BaTiO3 using Density Functional Theory (DFT), as well as pristine and fluorine-substituted BaTiO3 using reactive force-field molecular dynamics (ReaxFF-MD) simulations. DFT results for pristine and doped tetragonal BaTiO3, as well as pristine hexagonal BaTiO3, reveal that nitrogen and rhodium substitutions enhance the covalent character of Ti-N and Rh-O bonds and promote the redistribution of electron density, as evidenced by noncovalent interaction (NCI) and critical point (QTAIM) analyses, whereas fluorine substitution leads to more ionic Ti-F bonding. ReaxFF-MD simulations of pristine and fluorine-substituted BaTiO3 in contact with water molecules demonstrate that fluorine substitution suppresses interfacial O-H bond formation and promotes ordered molecular hydration layers near titanium sites, as reflected in bond statistics and radial distribution functions. This study provides molecular insights into the role of N, F, and Rh doping in BaTiO3 using DFT, and the role of fluorine doping in BaTiO3 at the water-solid interface using ReaxFF-MD simulations, demonstrating that this integrated computational approach provides a solid basis for the rational design of next-generation materials for energy-related applications. Direct calculations of photocatalytic activity, charge transfer rates, and ferroelectric polarization effects were not performed in this work and remain important directions for future study.

In this work, we performed a comprehensive first-principles investigation of the electronic structure, charge carrier relaxation dynamics, and photoluminescence properties of Rh-doped BaTiO3, with a focus on photocatalytic water splitting applications. By combining hybrid DFT (HSE06), DFT+U, and Redfield theory, we elucidated how the doping site (Ti vs. Ba), dimensionality (bulk vs. surface), and aqueous environment govern the nonequilibrium behavior of photogenerated electron-hole pairs. Rh occupying Ti sites on the (001) surface exhibits a unique combination of extended visible-light absorption, ultrafast non-radiative relaxation, and efficient charge separation. These characteristics establish it as a promising photoanode material for photoelectrochemical water splitting.

Photoinduced splitting of water using photocatalysts in the form of nanoparticles is a promising and simple way to produce environmentally friendly hydrogen. In this paper, we investigate the potential of modified barium titanate (BaTiO 3 ), an inexpensive perovskite oxide obtained from precursors widely distributed on earth, to develop effective electrocatalysts for water oxidation using first-principles calculations. It has been shown that the BaTiO 3 (001) surface terminated with TiO 2 is more promising in terms of its use as a catalyst. After replacing Ti with Rh, the dopant ion can take over part of the electron density from neighboring oxygen ions. As a result, during the oxidation reaction of water, rhodium ions can be in an intermediate oxidation state between 3+ and 4+. This affects the adsorption energy of the reaction intermediates on the surface of the catalyst, reducing the excess potential.

The optical properties of the tetragonal phase of BaTiO3 have been studied using the density functional method. In the study of a static lattice, we employed the generalized gradient approximation functional combined with on-site Hubbard correlation (GGA + U) and a hybrid functional. To account for the thermal motion of the atoms, we performed ab initio molecular dynamics calculations using the GGA + U method. We calculated the optical absorption spectra both for the static lattice and along the molecular dynamics trajectory. The results show that considering the motion of atoms leads to a significant decrease in the calculated value of the threshold energy for optical absorption. This effect occurs for two main reasons. First, changes in the atomic configuration due to thermal motion make electronic transitions that were previously dark for a static lattice become bright. Second, the optical absorption threshold decreases due to fluctuations in the energy of electronic transitions caused by the motion of atoms. The calculations were performed separately for different k-points of the Brillouin zone. The dispersion of electron energy in the reciprocal space may explain some features observed in the photoluminescence spectra.

We present a comprehensive first-principles study of the structural, electronic, and optical properties of [PO 4 ] 3– -substituted antizeolite borate materials based on the antizeolite borate crystal lattice. The substituted structures are found to be both mechanically and dynamically stable, as confirmed by compliance with Born stability criteria and ab initio molecular dynamics simulations up to 1200 K, with no bond rupture or atomic diffusion observed. The static DFT calculations show that [PO 4 ] 3– substitution slightly affects the optical absorption. However, finite-temperature effects revealed by molecular dynamics at 300 K dramatically alter the optical response: thermal lattice motion reduces symmetry, enhances oscillator strengths, and induces a red shift in absorption for [PO 4 ] 3– modified structures. In contrast, the oscillator strength in pristine antizeolite borate is strongly suppressed at finite temperature, explaining the accuracy of static calculations. Our results demonstrate that while [PO 4 ] 3– substitution has minimal impact on the static electronic structure, lattice vibrations at room temperature play a decisive role in shaping the optical properties, highlighting the importance of dynamic effects in the design and interpretation of spectroscopic behavior in complex borate materials.

In this article, the electronic and magnetic properties of half-Heusler alloys CrNiZ (Z = Sb, Sn) were investigated by a quantum chemical method based on density functional theory (DFT). Generalized gradient approximations (GGA) and meta-GGA exchange-correlation functionals (SCAN) were used in the calculations. According to the results obtained, it was found that while the CrNiSb alloy exhibits a half-metallic character, the CrNiSn alloy has a metallic character. The Meta-GGA (SCAN) functional was chosen as a method for a more accurate description of the electronic structure of CrNiZ alloys. In addition, it was found that the magnetic moment of the CrNiSb alloy is 3 µB, which corresponds to the Slater-Pauling rule.

Barium titanate (BaTiO3) has long been recognized as a promising photocatalyst for solar-driven water splitting due to its unique ferroelectric, piezoelectric, and electronic properties. This review provides a comprehensive analysis of atomistic simulation studies of BaTiO3, highlighting the role of density functional theory (DFT), ab initio molecular dynamics (MD), and classical all-atom MD in exploring its photocatalytic behavior, in line with various experimental findings. DFT studies have offered valuable insights into the electronic structure, density of state, optical properties, bandgap engineering, and other features of BaTiO3, while MD simulations have enabled dynamic understanding of water-splitting mechanisms at finite temperatures. Experimental studies demonstrate photocatalytic water decomposition and certain modifications, often accompanied by schematic diagrams illustrating the principles. This review discusses the impact of doping, surface modifications, and defect engineering on enhancing charge separation and reaction kinetics. Key findings from recent computational works are summarized, offering a deeper understanding of BaTiO3’s photocatalytic activity. This study underscores the significance of advanced multiscale simulation techniques for optimizing BaTiO3 for solar water splitting and provides perspectives on future research in developing high-performance photocatalytic materials.

In this study, a systematic investigation of the structural, electronic, and mechanical properties of CuNiZ (Z = Al, Ga, Sb, Sn) half-Heusler alloys was carried out based on density functional theory (DFT). The obtained results confirm the dynamical and mechanical stability of these alloys and provide insights into their structural symmetry and bonding nature. The electronic structure analysis revealed that CuNiZ alloys exhibit metallic behavior, while the calculated elastic moduli and Poisson's ratio characterize their mechanical strength. Furthermore, the calculations indicated the dominance of ionic bonding in these alloys and confirmed their compliance with fundamental mechanical stability criteria. The CuNiAl, CuNiSb, and CuNiSn alloys were found to be mechanically stable, with their anisotropy coefficients and other elastic parameters determined. This study demonstrates that CuNiZ half-Heusler alloys are promising candidates for functional materials. In particular, their mechanical robustness and structural properties make them potential candidates for applications in thermoelectric and spintronic devices.

The electronic, magnetic, elastic, and vibrational properties of new double half-Heusler (DHH) alloys V2Ni2Z′Z′′ are investigated within the density functional theory (DFT) calculations. All investigated alloys demonstrated mechanical, dynamic, and thermodynamic stability and complied with the Slater–Pauling rule. The analysis of their magnetic states indicates that all DHH alloys under investigation exhibit a ferromagnetic ground state. Electronic property analysis reveals that each alloy behaves as a half-metal, with an energy gap in the spin-up channel ranging from 0.103 to 0.653 eV. Based on the B/G ratio, the brittleness–ductility assessment yielded values around 2.5, indicating that alloys are ductile. The combination of magnetic properties, half-metallicity, and mechanical resilience makes these V2Ni2Z′Z′′ alloys promising candidates for high-performance spintronics devices and other advanced technological applications.

This research aimed to explore the structural, electronic, mechanical, and vibrational properties of double half Heusler compounds with the generic formula Ti2Pt2ZSb (Z = Al, Ga, and In), using density functional theory calculations. The generalized gradient approximation within the PBE functional was employed for structural relaxation and for calculations of vibrational and mechanical properties and thermal conductivity, while the hybrid HSE06 functional was employed for calculations of the electronic properties. Our results demonstrate that these compounds are energetically favorable and dynamically and mechanically stable. Our electronic structure calculations revealed that the Ti2Pt2AlSb double half Heusler compound is a non-magnetic semiconductor with an indirect band gap of 1.49 eV, while Ti2Pt2GaSb and Ti2Pt2InSb are non-magnetic semiconductors with direct band gaps of 1.40 eV. Further analysis, including phonon dispersion curves, the electron localization function (ELF), and Bader charge analysis, provided insights into the bonding character and vibrational properties of these materials. These findings suggest that double half Heusler compounds are promising candidates for thermoelectric device applications and energy-conversion devices, due to their favorable properties.

The advancement of effective, durable, and economically viable photocatalytic systems aimed at solar-driven water splitting into hydrogen and oxygen represents a strategically vital pathway for future fuel and chemical production from renewable sources. Water splitting is a promising strategy for the sustainable production of renewable hydrogen and for addressing the global energy and environmental crisis. However, the large-scale application of this method is limited by the low efficiency and high cost of solar water splitting systems. The search for economical, efficient, and stable photocatalysts is crucial in the development of solar water splitting technologies. Perovskite-based photocatalysts have recently attracted considerable attention for use in solar water splitting processes due to their simple structure and flexible composition. BaTiO 3 is a promising photocatalyst because of its adjustable electronic structure. Initially considered a poor photocatalyst due to its wide band gap, this material has become the focus of various strategies aimed at reducing the band gap. In this paper, we study the effect of Rh doping on the electronic structure of the (001) BaTiO 3 perovskite surface. Theoretical results show that Rh atoms can occupy both sites simultaneously, or only Ti sites, or Ba sites. The electronic structure was modeled for two conditions. When Rh atoms occupy one Ba position and one Ti position, the electronic structure shows the presence of an acceptor level within the band gap above the Fermi level, effectively reducing the band gap of the material.

This study presents theoretical and experimental investigations into the electron and hole color centers in BaFBr crystals, characterizing their electronic and optical properties. Stoichiometric BaFBr crystals grown by the Steber method were used in the experiments. Radiation defects in BaFBr crystals were created by irradiation with 147 MeV 84Kr ions with up to fluences of 1010–1014 ions/cm2. The formation of electron color centers (F(F−), F2(F−), F2(Br−)) and hole aggregates was experimentally established by optical absorption spectroscopy. Performed measurements are compared with theoretical calculations. It allows us to determine the electron transition mechanisms and investigate the processes involved in photoluminescence emission in Eu-doped BaFBr materials to enhance the understanding of the fundamental electronic structure and properties of electron and hole color centers formed in BaFBr crystals.

The accurate prediction of bandgap energy Eg is crucial for the future development of semiconductors. Ab initio simulation studies have been undertaken to unravel the intricacies of compound semiconductors. However, traditional density functional theory estimates Eg to be mostly 30-50% smaller than experimental values. To reconcile these disparities, fitting parameters such as U have been employed, albeit at the expense of violating the virial theorem's essential conditions. In our pursuit of a more accurate approach, utilizing a computational method that adheres to virial's theorem without resorting to fitting parameters is proposed. Employing the self-consistent Green-function vertex (GW) approximation calculation, standard phenomenological results are built upon as an initial condition. This novel methodology successfully resolves the long-standing issue surrounding Eg of InN, a nitride semiconductor InGaAlN known for blue light-emitting diodes. The numerical results from our calculations demonstrate a remarkable alignment with experimental values across the entire InxGa1-xN range, with an impressive accuracy of 0.1 eV. This innovative method holds promise for application to various semiconductors, serving as a potent tool for predicting new semiconductors with small Eg. This calculation method is also applied to Eg of In1-xAlxN and Ga1-xAlxN.

In the present work, we investigate the potential of modified barium titanate (BaTiO3), an inexpensive perovskite oxide derived from earth-abundant precursors, for developing efficient water oxidation electrocatalysts using first-principles calculations. Based on our calculations, Rh doping is a way of making BaTiO3 absorb more light and have less overpotential needed for water to oxidize. It has been shown that a TiO2-terminated BaTiO3 (001) surface is more promising from the point of view of its use as a catalyst. Rh doping expands the spectrum of absorbed light to the entire visible range. The aqueous environment significantly affects the ability of Rh-doped BaTiO3 to absorb solar radiation. After Ti→Rh replacement, the doping ion can take over part of the electron density from neighboring oxygen ions. As a result, during the water oxidation reaction, rhodium ions can be in an intermediate oxidation state between 3+ and 4+. This affects the adsorption energy of reaction intermediates on the catalyst’s surface, reducing the overpotential value.

Barium titanate is one of the most studied perovskite materials due to its substitution ability at both nodes of the crystal lattice, high dielectric constant, and stability. It has many outstanding characteristics, especially ferroelectric and dielectric properties, which can be improved by alloying, making this material suitable for a wide range of applications. In this paper, the effect of Rh doping on the structural, optical properties and electronic density of states of this compound is investigated. According to our calculations, Rh doping is a method that helps to increase the ability of BaTiO 3 to absorb more light and reduce the excess potential required for water oxidation. Calculations of the electronic density of states were carried out using the hybrid functional HSE06. The analysis of optical properties was performed on the basis of matrix elements with a transient dipole moment. Studies have confirmed that the (001) BaTiO 3 surface with terminated TiO 2 has significant potential for use as a catalyst. Rh doping leads to an expansion of the spectrum of absorbed light over the entire visible range.

The stability of CO2 phases at pressures up to 1600 GPa is confirmed using evolution methods for predicting crystal structures. Stable CO2 phases are as follows: I4̅2d (to 279 GPa), P4_2/nmc (279–952 GPa), Pbcn (952–1018 GPa), and Pa3̅ (above 1018 GPa). The equations of state for stable CO2 phases up to pressures of about 1600 GPa are calculated for the first time using ab initio methods and high-temperature calculations within the quasi-harmonic approximation. It is shown that high-pressure P4_2/nmc , Pbcn , and Pa3̅ phases have rather high bulk moduli (290–415 GPa). Phases with sixfold coordination of carbon atoms (Pbcn and Pa3̅ ) have higher coefficients of thermal expansion in comparison with the P4_2/nmc phase.

Antizeolite fluoride borates LiBa12(BO3)7F4 (LBBF) doped by Ce3+ ions demonstrate photoluminescence (PL) and hold promise for use as phosphors in white light-emitting diodes. In this study, we present the results of modeling the electronic and optical properties of Ce-containing LBBF structures where doping atoms are located at different sites of the host lattice. We also consider the presence of F-centers, which exhibit trap states located within the band gap. We further investigate the nonadiabatic excited state electronic dynamics to elucidate electron-relaxation pathways. The nonadiabatic couplings (NACs) calculations provide transition probabilities facilitated by the nuclear movement. The relaxation rates of electrons and holes are calculated using Redfield's theory of the formalism of the reduced density matrix (RDM). The PL spectra are calculated using molecular dynamics (MD) sampling and time-integrated methods along the excited state trajectory based on NACs. Mechanisms of PL in LBBF:Ce3+ crystals are interpreted using both computational and experimental observations. This work illustrates the dependence of transition energies, intensities, and relaxation rates of Ce-containing LBBF crystals on a selection of doping sites. In addition to analysis of emission band contributed by cerium, this work allows to identify and reproduce spectral lines hypothetically corresponding to the interband and intraband transitions in F-centers of borate crystals, available in the absence of a metal center.

The characteristics related to electricity and magnetism in Heusler alloys with both full (L21) and inverse (XA) structures X2FeSi (X = Mn, V) have been studied within the framework of the Density Functional Theory. Three different methods, namely LDA, GGA, and SCAN, were used to perform calculations. The aim was to investigate the energy stability of the L21 and XA structures for these compositions. The findings revealed that the XA structure is energetically stable for both structures. The choice of functional is indicated does not have a qualitative effect on the energy stability of the phases. Based on calculations, it was found that meta-GGA (SCAN) more accurately describes the electronic properties of these alloys. In the process of the calculations, it was found that these compounds are semimetals. An analysis was conducted from a local environment perspective to investigate and understand the reasons behind the semi-metallic band gap and the variations in electronic and magnetic properties observed in Heusler compounds. Calculations also showed that the magnetic moment Mn2FeSi for both structures was 1.99 µB/f.u. With regard to V2FeSi, µ = 2.00 µB/f.u. for structure XA and µ = 2.37 µB/f.u. for structure L21. These calculations are consistent with the Slater-Pauling rule for the XA structure.

The characteristics related to electricity and magnetism in Heusler alloys with both full (L 2 1) and inverse (XA) structures X 2 FeSi (X = Mn, V) have been studied within the framework of the Density Functional Theory. Three different methods, namely LDA, GGA, and SCAN, were used to perform calculations. The aim was to investigate the energy stability of the L 2 1 and XA structures for these compositions. The findings revealed that the XA structure is energetically stable for both structures. The choice of functional is indicated does not have a qualitative effect on the energy stability of the phases. Based on calculations, it was found that meta-GGA (SCAN) more accurately describes the electronic properties of these alloys. In the process of the calculations, it was found that these compounds are semimetals. An analysis was conducted from a local environment perspective to investigate and understand the reasons behind the semi-metallic band gap and the variations in electronic and magnetic properties observed in Heusler compounds. Calculations also showed that the magnetic moment Mn 2 FeSi for both structures was 1.99 µ B /f.u. With regard to V 2 FeSi, µ = 2.00 µ B /f.u. for structure XA and µ = 2.37 µ B /f.u. for structure L 2 1. These calculations are consistent with the Slater-Pauling rule for the XA structure.