The influence of electronic many-body interactions, spin-orbit coupling, and thermal lattice vibrations on the structure lithium niobate is calculated from first principles. Self-energy calculations in $GW$ approximation show that inclusion self-consistency Green function $G$ screened Coulomb potential $W$ opens band gap far stronger than found previous ${G}_{0}{W}_{0}$ but slightly overestimates its actual value due to neglect excitonic effects $W$. A realistic frozen-lattice about 5.9 eV...

The quasiparticle band structures and fundamental energy gaps of the rock-salt ($rs$), zinc-blende ($zb$), wurtzite ($wz$) polymorphs CaO AlN are calculated within ${G}_{0}{W}_{0}$ approximation on top a self-consistent solution generalized Kohn--Sham equation with hybrid functional HSE03. Based these reliable electronic structures, dielectric functions $rs$-CaO, $zb$-AlN, $wz$-AlN including excitonic effects obtained from Bethe--Salpeter equation. peaks in absorption spectra analyzed terms...

The frequency-dependent dielectric function and the second-order polarizability tensor of ferroelectric ${\mathrm{LiNbO}}_{3}$ are calculated from first principles. calculations based on electronic structure obtained density-functional theory. subsequent application $GW$ approximation to account for quasiparticle effects solution Bethe-Salpeter equation stoichiometric material yield a that slightly overestimates absorption onset oscillator strength in comparison with experimental...

The vibrational properties of stoichiometric LiNbO3 are analyzed within density-functional perturbation theory in order to obtain the complete phonon dispersion material. density states ferroelectric (paraelectric) phase shows two (one) distinct band gaps separating high-frequency (∼800 cm(-1)) optical branches from continuum acoustic and lower states. This result leads specific heat capacites close agreement with experimental measurements range 0-350 K a Debye temperature 574 K. calculated...

The adsorption of single methanol molecules on the lithium niobate (0001) surface, commonly referred to as Z-cut, is investigated using first-principles calculations. It found that binding energy for molecular negative surface ($\ensuremath{\sim}$1 eV) about twice large positive surface. This difference related different bond strengths rather than electrostatics. Depending reaction path, extraction from may occur. leads an additional lowering by a few tenths eV. Larger gains are realized...

The iron(III) complexes [Fe(H2O)n(OH)m]3−m (n + m = 5, 6, ≤ 3) and corresponding proton transfer reactions are studied with total energy calculations, the nudged elastic band (NEB) method, molecular dynamics (MD) simulations using ab initio a modification of reactive force field potentials, ReaxFF-AQ based on implementation according to Böhm et al. [J. Phys. Chem. C 120, 10849–10856 (2016)]. Applying energies for H2O → [Fe(H2O)n−1(OH)m+1]2−m H3O+ in gaseous environment good agreement...

The cubic, tetragonal, and orthorhombic phase of potassium niobate (${\mathrm{KNbO}}_{3}$) are studied based on density-functional theory. Starting from the relaxed atomic geometries, we analyze influence self-energy corrections electronic band structure within $GW$ approximation. We find that quasiparticle shifts widen direct (indirect) gap by 1.21 (1.44), 1.58 (1.55), 1.67 (1.64) eV for phase, respectively. By solving Bethe-Salpeter equation, obtain linear dielectric function with...

The influence of excitonic and local-field effects on the second-harmonic-generation spectrum zinc-blende ZnS, ZnSe, ZnTe is studied from first principles using Bethe-Salpeter equation. calculations are based theory R. Leitsmann et al. [Phys. Rev. B 71, 195209 (2005)], which we extended to low-frequency range. dielectric function have been obtained within independent (quasi)particle approximation approach. demonstrate that linear nonlinear optical properties similarly affected by effects....

A variety of fluoroarene-2-aminopyrimidine (FAP) silver(I) coordination polymers (CPs) has been synthesized based on newly FAP derivatives, namely 5-(p-methoxytetrafluorophenyl)-2-aminopyrimidine (OFAP) and 5-(p-dimethylaminotetrafluorophenyl)-2-aminopyrimidine (NFAP), different counterions (OTf−, TFA−, ClO4−, NO3−). Their solid-state assembly as well optical properties in terms luminescence infrared (IR) spectroscopy were investigated. Out the several structures described herein, we...

Calculations based on (occupation constrained) density functional theory using local as well hybrid functionals to describe the electron-electron exchange and correlation are combined with many-body perturbation in order determine rationalize electronic optical excitation properties of 2-aminopyrimidine-silver(I) organic semiconductors their parent molecules. Large quasiparticle shifts exciton binding energies about 4 eV found aminopyrimidine Both blueshift excitonic redshift reduced upon...

Abstract Atomistic simulations in the framework of density functional theory have been used to model morphologic and vibrational properties lithium niobate–lithium tantalate mixed crystals as a function [Nb]/[Ta] ratio. Structural parameters such crystal volume lattice c vary roughly linearly from LiTaO3 LiNbO3, showing only minor deviations Vegard behavior. Our ab initio calculations demonstrate that TO1, TO2 TO4 modes become harder with increasing Nb concentration. TO3 becomes softer...

The dielectric function and second-harmonic generation spectrum of ferroelectric LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> are calculated from first principles. calculations based on the electronic structure obtained within density functional theory. use GW approach to account for quasiparticle effects subsequent solution Bethe-Salpeter equation lead a in excellent agreement with measured data. second harmonic independent...

Ab-initio methods are applied to investigate the electronic and optical properties of lithium niobate-tantalate mixed crystals. Thereby GW approach based on structure obtained within density functional theory is used obtain electron band including quasi-particle effects linear response gained form solution Bethe-Salpeter equation taking excitonic local-field into account. Nonlinear coefficients evaluated level independent-particle approximation. It observed that increasing tantalum amount...

The removal of the anodic material within electrochemical machining (ECM) processes is a consequence reactions taking place at interface between metal and electrolyte. For iron-based materials an iron-oxide layer emerges to details about electrolyte responsible for dissolution iron into are not fully understood. Considering that lack knowledge, aim present study gain insights in atomistic interactions with subjected electric field. One main purpose use molecular dynamics simulations ReaxFF+...

The electronic band structures of hexagonal ZnO and cubic ZnS, ZnSe, ZnTe compounds are determined within hybrid-density-functional theory quasiparticle calculations. It is found that the band-edge energies calculated on [Formula: see text] (Zn chalcogenides) or GW (ZnO) level agree well with experiment, while fully self-consistent QSGW calculations required for correct description Zn 3d bands. used to calculate linear response second-harmonic-generation (SHG) spectra Zn-VI compounds....

The electronic and optical properties of the mixed-crystal system lithium niobate-tantalate has been calculated from first principles. Based on density functional theory we calculate including quasiparticle effects within GW approach. response electron-hole attraction is obtained solution Bethe-Salpeter equation. While band gap increase with increasing tantalum content shows some bowing, a nearly linear dependence birefringence stochiometry calculated.

The structural and vibrational properties of lithium niobate (LN) - tantalate (LT) mixed crystals (LNT, LiNb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">1-x</sub> Ta xmlns:xlink="http://www.w3.org/1999/xlink">x</sub> O xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> ) are investigated over the whole composition range by first-principles simulations. crystal volume grows roughly linearly from LT to LN, whereby lattice parameters a c show...

The dielectric function and second harmonic generation of ferroelectric LiNbO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> is calculated from first-principles. Thereby we start the electronic structure within density functional theory. use GW approach to account for quasiparticle effects subsequent solution Bethe-Salpeter equation leads a that in excellent agreement with available experimental results. Our calculations rest on...