We present first-principles calculations of the thermodynamic and structural properties cubic ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ ${\mathrm{Al}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ alloys. They are based on generalized quasichemical approach to disorder composition effects a pseudopotential-plane-wave approximation for total energy. The cluster treatment is study influence biaxial strain. find remarkable suppression phase separation in...

The electronic band structures of silicon and the zinc-blende-type III-N semiconductor compounds BN, AlN, GaN, InN are calculated by using self-consistent full potential linear augmented plane wave method within local-density functional approximation. Lattice constant, bulk modulus, cohesive energy obtained from relativistic total-energy calculations for Si nitrides. Band total density states (DOS) presented. role played effects on DOS is discussed. In order to provide important...

Structural, electronic, and optical properties for the cubic, tetragonal, monoclinic crystalline phases of ZrO2, as derived from ab initio full-relativistic calculations, are presented. The electronic structure calculations were carried out by means all-electron full-potential linear augmented plane wave method, within framework density functional theory local approximation. calculated carrier effective masses shown to be highly anisotropic. results obtained real imaginary parts dielectric...

Phase separation suppression due to external biaxial strain is observed in InxGa1−xN alloy layers by Raman scattering spectroscopy. The effect taking place thin epitaxial pseudomorphically grown molecular-beam epitaxy on unstrained GaN(001) buffers. Ab initio calculations carried out for the free energy predict and measurements confirm that suppress formation of phase-separated In-rich quantum dots layers. Since are effective radiative recombination centers InGaN, we conclude quenches an...

We present ab initio calculations of the electronic structure and optical properties InxGa1–xN. They are completed by studies strain influence on alloys. The results critically discussed in light recent experiments. find an energy gap InN < 1 eV a nonparabolic absorption edge. strong variation alloy with In molar fraction is described composition-dependent bowing parameter. tendency spinodal decomposition suppressed biaxial strain. Its extent depends realization accommodation.

We report on x-ray diffraction and micro-Raman scattering studies zinc blende InN epitaxial films. The samples were grown by molecular beam epitaxy GaAs(001) substrates using a InAs layer as buffer. transverse-optical (TO) longitudinal-optical phonon frequencies at Γ of c-InN are determined compared to the corresponding values for c-GaN. Ab initio self-consistent calculations carried out c-GaN lattice parameters TO frequencies. A good agreement between theory experiment is found.

First-principles total energy calculations, combined with a generalized quasichemical approach to disorder and compositional effects, are used obtain the lattice parameter band gap of cubic AlxGayIn1−x−yN quaternary alloys. It is found that a(x,y) fulfills Vegard’s-like law; is, it shows linear dependence on alloy contents x y. The range compositions for which lattice-matched GaN obtained. Eg(x,y) deviates from planar behavior displaying two-dimensional bowing in x–y plane. Analytical...

The outstanding physical and chemical properties of the magnesium aluminate (MgAl2O4) spinel makes it an important material for novel technological applications. Considering that a presence native defects can promote changes in those properties, this work we present study structural, electronic thermodynamic MgAl2O4 spinel. calculated formation energy isolated defects, such as vacancies (VMg), aluminum (VAl) oxygen (VO), interstitial (Oi), antisites (MgAl, AlMg), well some complex (VO + Oi,...

Abstract Indium defects in small concentration (In x Ga 1− ) 2 O 3 were studied using a combination of spectroscopic and magnetic measurements on thin films varying the indium concentration, coupled with hybrid density functional theory simulations supercell method. X-ray diffraction spectra along Tauc plots states reveal decrease (increase) electronic band gap (interlayer lattice spacing) due to inclusion monoclinic , while room-temperature Hall show an increase n-type conductivity....

We perform fully relativistic band-structure calculations for cubic SrTiO3, which are used to obtain carrier effective masses and the frequency behavior of its complex dielectric function ε(ω). The obtained values anisotropy shown be highly influenced by contributions. In order evaluate static constant, low-frequency ε(ω) is taking into account also optical phonon contributions imaginary part ε(ω), adopting a simplified classical oscillator dispersion model. It found that contribution leads...

We investigate the possible formation of polarons in four organic perovskites (CH3NH3PbI3, CH3NH3PbBr3, CH3NH3PbCl3, and CH3NH3PbI2Cl1) using a density functional theory (DFT) calculations with local potentials hybrid functionals. show that DFT+U method U = 8 eV predicts correct band-gap matches forces on ions from calculations. then use DFT + approach to study effect polarons, i.e. search configuration space locate lowest energy localized band gap state self-trapped hole (STH). STH...

We present first-principles calculations of the structural and thermodynamic properties cubic BxGa1−xN BxAl1−xN alloys. The are based on generalized quasichemical approach to disorder composition effects a pseudopotential-plane-wave approximation. bulk moduli lattice constants found vary linearly with alloy composition. Due large mismatch between BN binaries GaN AlN, phase diagrams display miscibility gaps in temperature range usually adopted grow corresponding This explains difficulties...

p-type \ensuremath{\delta}-doping quantum wells and superlattices are semiconductor systems of considerable interest for basic research device applications. In this paper, a method calculating potentials band structures such is developed. The relies on plane-wave expansion the multiband effective-mass equation, uses kinetic energy matrices any size, takes exchange correlation into account in more rigorous way than was done before. used to calculate potential profiles, subband miniband...

Light absorption of $\ensuremath{\alpha}$-glycine crystals grown by slow evaporation at room temperature was measured, indicating a $5.11\ifmmode\pm\else\textpm\fi{}0.02\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$ energy band gap. Structural, electronic, and optical properties were obtained first-principles quantum mechanical calculations using density functional theory within the generalized gradient approximation in order to understand this result. To take into account contribution core...

The observation of quantum-confined optical transitions in multiple δ doping GaAs, grown by molecular beam epitaxy, is reported. Doping efficiency and carrier confinement are investigated Hall photoluminescence measurements. measurement results for δ-doped samples show a dramatic enhancement concentrations compared to the uniform case. From spectra we observed that cutoff energy significantly affected spacing between dopant sheets. strong localization confined photoexcited holes layers these...

The electronic band structure of cubic HfO2 is calculated using an ab initio all-electron self-consistent linear augmented plane-wave method, within the framework local-density approximation and taking into account full-relativistic contributions. From structure, carrier effective masses complex dielectric function are obtained. Γ-isotropic heavy light electron shown to be several times heavier than tunneling mass measured recently. imaginary part ϵ2(ω) in good agreement with experimental...

We present ab initio pseudopotential plane-wave calculations for the neutral and negatively charged carbon impurity on a nitrogen site in group-III nitrides. Ultrasoft non-norm-conserving Vanderbilt pseudopotentials allow use of extremely large supercells up to 2744 atoms. These attenuate defect-defect interaction and, hence, give an accurate description resulting acceptor levels BN, AlN, GaN, InN. calculate atomic geometries energetical positions defect levels, Franck-Condon shifts,...

We present parameter-free calculations of electronic properties ${\mathrm{In}}_{x}{\mathrm{Ga}}_{1\ensuremath{-}x}\mathrm{N}$ alloys based on a generalized quasichemical approach and pseudopotential-plane-wave method. The gap fluctuations in the alloy allow definition minimum an average with different bowing parameters. Biaxial strain drastically reduces fluctuations, resulting reduction bowing. gaps influence investigated here provide explanation for discrepancies found experimental values...

For manganese mononitride (MnN), the total energy versus lattice constant is obtained using spin density functional theory. Instead of tetragonally distorted NaCl structure, we study zinc blende and wurtzite structures in which AlN, GaN, InN crystallize. The ground state with nonmagnetic, antiferromagnetic (AFM), or ferromagnetic (FM) arrangement spins depends on polymorph MnN constant. At equilibrium constants, it AFM [100] direction, FM. polytype under hydrostatic pressure at presents FM...

The phonon dispersion and the lattice contribution to dielectric function of PbTe in NaCl structure are calculated ab initio. results obtained agreement with available experimental data reproduce main features observed this material, such as an anharmonic LA-TO coupling $\ensuremath{\Gamma}$-X direction, well high values for constants ${\ensuremath{\epsilon}}_{1}(0)$ ${\ensuremath{\epsilon}}_{1}(\ensuremath{\infty})$. Calculations include pressure dependence indicate that is very sensitive...

The electronic subband structure of periodically n-type \ensuremath{\delta}-doped silicon is calculated self-consistently within the local-density approximation. Two types energy levels are distinguished, one due to valleys transverse superlattice axis, and other longitudinal valleys. Minibands, potential profiles, miniband occupancies, Fermi-level positions studied their dependence on spacing d between \ensuremath{\delta} layers doping concentration ${\mathit{N}}_{\mathit{D}}$ obtained....

Thermodynamic, structural, and electronic properties of cubic InxAl1−xN alloys are studied by combining first-principles total energy calculations the generalized quasichemical approach. Results for bond-lengths, second-nearest-neighbors distances, bond angles in alloy presented. The calculated phase diagram shows a broad asymmetric miscibility gap. gap fluctuations allow definition minimum an average with different bowing parameters, that can provide explanation discrepancies found...