Bahattin Erdinc

Ab-initio study of the electronic structure and optical properties of KNO3 in the ferroelectric phase

The electronic band structure and optical properties of the ferroelectric phase III of KNO3 have been investigated by the first-principle pseudopotential method using the density functional theory under the generalized gradient approximation (GGA) and local density approximation (LDA). The calculated band structure shows that the ferroelectric phase III of KNO3 has a direct band gap with a value of 1.76 eV at the point of the first Brillouin zone (BZ). The structural optimization of KNO3 has been performed using the GGA and LDA. The results of the structure optimization have been compared with the experimental results and have been found to be in good agreement with these results. Moreover, the linear photon-energy-dependent dielectric functions and some optical constants such as energy-loss functions for volume and surface, extinction, reflectivity and absorption coefficients, refractive index and effective number of valance electrons per unit cell participating in the interband transitions have been calculated.

Structural and electronic properties of zincblende phase of TlxGa1−x AsyP1−y quaternary alloys: First-principles study

Using the first-principles band-structure method, we have calculated the structural and electronic properties of zincblende TlAs, TlP, GaAs and GaP compounds and their new semiconductor TlxGa1−xAsyP1−y quaternary alloys. Structural properties of these semiconductors are obtained with the Perdew and Wang local-density approximation. The lattice constants of TlxGa1−xAs, TlxGa1−xP ternary and TlxGa1−xAsyP1−y quaternary alloys were composed by Vegard’s law. Our investigation on the effect of the doping (Thallium and Arsenic) on lattice constants and band gap shows a non-linear dependence for TlxGa1−xAsyP1−y quaternary alloys. The band gap of TlxGa1−xAsyP1−y, Eg(x, y) concerned by the compositions x and y. To our awareness, there is no theoretical survey on TlxGa1−xAsyP1−y quaternary alloys and needs experimental verification.

First-principles investigation of structural, electronic, optical and dynamical properties in CsAu

The structural, electronic, optical and dynamical properties of CsAu compound in the CsCl(B2) phase were investigated using the density functional theory (DFT) within the generalized gradient approximation (GGA). The calculated lattice constant, static bulk modulus and first-order pressure derivative of the bulk modulus are reported and compared with previous experimental and theoretical calculations. The calculated electronic band structure for this compound is in good agreement with available theoretical and experimental studies. The present band calculation indicates that CsAu compound has an indirect gap at R→X points. Furthermore, the linear photon-energy-dependent dielectric functions have been calculated. For the first time, the electronic structure results are used, within the implementation of a linear-response technique, for calculations of phonon properties.

Ab-initio study of CsGeCl3 compound in paraelectric and ferroelectric phases

ABSTRACT Structural optimization, electronic energy band structure, density of states, optical, lattice dynamic and thermodynamic properties of CsGeCl3 compound in paraelectric and ferroelectric phases were investigated using the DFT in the GGA and LDA approximations. The obtained results of CsGeCl3 crystal were compared with the available theoretical and experimental results and have been found to be in good agreement with these results.

Linear Optical Properties of Ferroelectric Semiconductor Bi2NbO5F Crystal

In this paper, we investigated the electronic band structure, total and partial density of states and optical properties of ferroelectric Bi2NbO5F structure with space group Pca21 using the density functional theory under the generalized gradient approximation. Our computational results show that Bi2NbO5F compound is a ferroelectric semiconductor with a narrow band gap. Due to anisotropy, linear optical properties of component were calculated for three crystallographic directions.

First-principles study of electronic and optical properties of cubic AgTaO3 structure in paraelectric phase at different pressures

ABSTRACT In the present article, a theoretical study of structural properties, energy band structure, total (TDOS) and partial (PDOS) density of states, real and imaginary parts of photon frequency dependent complex dielectric function of cubic AgTaO3 in paraelectric phase was presented by ab-initio calculations using DFT-LDA in the ABINIT code. The obtained energy band structure under various pressures shows that AgTaO3 has an indirect band gap at the Γ and M points in the first Brillouin zone which increases by increasing pressure. Calculated results for energy band gap and optical properties under pressure are given and these results were compared with the experimental results and previous calculations.

FIRST PRINCIPLE CALCULATION OF ELECTRONIC BAND STRUCTURE AND OPTICAL PROPERTIES OF KIO3

The electronic band structure and optical properties of the ferroelectric single crystal KIO3 have been investigated using the density functional methods. The calculated band structure for KIO3 evidences that the crystal has a direct band gap with a value of 2.83 eV. The structural optimization has been performed. The real and imaginary parts of dielectric function, energy-loss function for volume and surface, and refractive index are calculated along the crystallographic axes.