Investigation of electronic and linear optical properties of NaTaO3 crystal

In this dissertation, the structural (lattice parameters and atomic positions), electronic energy band structure, density of states (DOS) and optical properties of NaTaO3 crystal in the paraelectric cubic (Pm m), tetragonal (P4/mbm) and orthorhombic (Pcmn) phase were investigated by using density functional theory within the local density approximation for exchange-correlation. The optical and electronic properties of tetragonal phase of NaTaO3 were investigated by theoretical for first time. The band structure shows an indirect band gap 2,183 eV (cubic phase) at (R-?) point, 2,230 eV (tetragonal phase) at (Z- ? ) point, and a direct band gap 2,231 eV (orthorhombic phase) at (?-?) point in the Brillouin zone. The linear photon-energy dependent dielectric functions and some optical properties such as the absorption coefficient, energy-loss function and reflectivity are calculated under the scissor approximation for NaTaO3. The effective number of valence electrons is calculated for three phases. We have also made some comparisons with related experimental and theoretical data which is available.