The first-principles (ab initio) computations of the structural, electronic, and phonon properties have been performed for cubic low-temperature tetragonal phases BaTiO3 SrTiO3 perovskite crystals, both stoichiometric non-stoichiometric (with neutral oxygen vacancies). Calculations were with CRYSTAL17 computer code within linear combination atomic orbitals approximation, using B1WC advanced hybrid exchange-correlation functional density-functional-theory (DFT) periodic supercell approach....

A noticeable improvement of hydrogen production upon photocatalytic water splitting was found recently experimentally on the faceted nanoparticles strontium titanate (SrTiO3, STO). In this paper, we study and theoretically effects Al doping electronic structure, optical properties, efficiency. It is demonstrated here that significantly increases photoactivity in splitting. The preparation Al-doped STO photocatalysts molten KCl with further optimization synthesis procedure co-catalyst...

The results of first-principles calculations the structural, electronic, elastic, vibrational, dielectric and optical properties, as well Raman infrared (IR) spectra, potassium hexafluorosilicate (K2SiF6; KSF) crystal are discussed. KSF doped with manganese atoms (KSF:Mn4+) is known for its ability to function a phosphor in white LED applications due efficient red emission from Mn⁴⁺ activator ions. simulations were performed using CRYSTAL23 computer code within linear combination atomic...

The results of experimental and theoretical ab initio study structural piezoelectric properties (Ba,Sr)TiO3 perovskite solid solutions are discussed compared. Experimentally, plate-like particles were synthesized by the topochemical conversion in molten salt from Bi4Ti3O12 template plates. All dimensions (side length ≈1 μm, thickness ≈200–400 nm) well above critical size necessary for observation piezo- ferroelectricity. first-principles computations electromechanical performed with...

The role of stochastization magnetic field lines is analysed in fast reconnection phenomena occurring magnetized fusion plasma during various conditions the ASDEX Upgrade tokamak. mapping technique applied to trace toroidally confined where perturbation parameters are expressed terms experimental amplitudes determined from It found that observed amplitude drops neoclassical tearing mode instability frequently interrupted regime can be related stochastization. also shown explain loss...

An enhancement of the piezoelectric properties lead-free materials, which allow conversion mechanical energy into electricity, is a task great importance and interest. Results first-principles calculations piezoelectric/electromechanical Ba(1-x)SrxTiO3 (BSTO) ferroelectric solid solution with perovskite structure are presented discussed. Calculations performed within linear combination atomic orbitals (LCAO) approximation periodic-boundary conditions, using advanced hybrid functionals...

We present the results of a detailed first principles study piezoelectric properties (SrTiO3)m/(BaTiO3)M-m heterostructure using 3D STOm/BTOM-m superlattice model. The atomic basis set, hybrid functionals and slabs with different numbers STO BTO layers were used. interplay between ferroelectric (FEz) antiferrodistortive (AFDz) displacements is carefully analyzed. Based on experimental data group theoretical analysis, we deduce two possible space groups tetragonal symmetry which allow us to...

The colloidal processing of nearly monodisperse and highly crystalline single-domain ferroelectric or ferromagnetic nanocubes is a promising route to produce superlattice structures for integration into next-generation devices, whereas controlling the local behaviour nanocrystals imperative fabricating highly-ordered assemblies. current picture nanoscale polarization in individual suggests potential presence significant dipolar interaction, but its role condensation unknown. We simulate...

We present theoretical justification for distorted Ruddlesden-Popper (RP) phases of the first-order by using hybrid density functional theory (DFT) calculations and group-theoretical analysis. We, thus, demonstrate existence Jahn-Teller effect around an Fe[Formula: see text] ion in Sr[Formula: text]FeO[Formula: text]. On calculation side, we have established a combination Wu-Cohen (WC) exchange Perdew-Wang (PW) correlation three-parameter WC3PW, giving most accurate description from...

The standard Lotka-type model, which was introduced for the first time by Mai et al. [J. Phys. A 30, 4171 (1997)] a simplified description of autocatalytic surface reactions, is generalized here case mobile and energetically interacting reactants. mathematical formalism proposed determining dependence transition rates on interaction energy (and temperature) general in particular. By means Monte Carlo computer simulations, we have studied impact diffusion (with without energetic interactions...

Recent experimental findings suggest that strontium titanate SrTiO3 (STO) photocatalytic activity for water splitting could be improved by creating multifaceted nanoparticles. To understand the underlying mechanisms and energetics, model faceted nanoparticles was created. The nanoparticles’ surface is considered us as a combination of flat “stepped” facets. Ab initio calculations adsorption oxygen evolution reaction (OER) intermediates were performed. Our “slope” part step showed natural...

A microscopic formalism based on computing many-particle densities is applied to the analysis of diffusion-controlled kinetics pattern formation in oppositely charged molecules surfaces or adsorbed at interfaces with competing long-range Coulomb and short-range Lennard-Jones interactions. Particular attention paid proper molecular treatment energetic interactions driving inhomogeneous systems. The reverse Monte Carlo method used visualize spatial distribution calculated radial functions...

An approach to analysis of time series edge localized modes (ELMs) is proposed. It based on the use autoregressive moving average model, which decomposes into deterministic and noise components. Despite inclusion nonlinearity in resulting equations for ELM measured Axially Symmetric Divertor Experiment Upgrade tokamak turn out be linear. This contrasts with findings JAERI (JT-60U) à configuration variable that ELMs exhibit features chaotic dynamics, namely, presence unstable periodic orbits....

The 3d structure of self-assembled and oppositely charged nanoparticles.

Abstract Recent research suggests that photocatalytic activity toward water splitting of strontium titanate SrTiO 3 (STO) is enhanced by creating multifaceted nanoparticles. To better understand the source this activity, a previously designed model used for two types surfaces nanoparticle, flat and double‐stepped. Density functional theory calculations adsorption on these are performed to gain insight into proton migration processes, as well thermodynamics hydrogen evolution reaction within...

While the bulk strontium titanate (STO) crystal characteristics are relatively well known, ultrathin perovskites' nanostructure, chemical composition, and crystallinity quite complex challenging to understand in detail. In our study, DFT methods were used for modelling Raman spectra of STO (space group I4/mcm) 5-21-layer thin films (layer p4/mbm) tetragonal phase with different thicknesses ranging from ~0.8 3.9 nm. Our calculations revealed features that absent spectra. Out seven...

The kinetics of mesoscopic pattern formation is studied for a reversible $A+B \rightleftharpoons 0$A+B⇌0 reaction between mobile oppositely charged molecules at the interface. Using formalism joint correlation functions, non-equilibrium charge screening and reverse Monte Carlo methods, it shown that labyrinth-like percolation structure induced by (even moderate-rate) principally non-steady-state one associated with permanently growing segregation dissimilar reactants aggregation similar into...

The kinetics of pattern formation and phase separation in a system two types oppositely charged molecules with competing short- long-range interactions on surfaces/interfaces is studied combining three methods: microscopic formalism the joint correlation functions, reverse Monte Carlo, nonequilibrium charge-screening factors. molecular ordering occurs background Ostwald ripening thus strongly nonequilibrium. We have demonstrated how initial random distribution changed for loose...