First principles study of electronic band structure and optical properties of (SrTiO3-SrZrO3) some quasi crystals

In this dissertation, the structural (lattice parameters and atomic positions), the electronic band structures, density of states (DOS) and optical properties of ABO3 -type ternary compounds, SrTiO3 and SrZrO3, in the cubic Pm3m (No:221) are investigated by using the density functional theory (DFT) and ab-initio pseudopotential method within the Generalized Gradient Approximation (GGA). The obtained electronic band structure shows that SrTiO3 and SrZrO3 crystals have an indirect forbidden band gap of for SrTiO3, 2.3134 eV at the R-? point and for SrZrO3, 3.5702 eV at the R-? point of the Brillouin zone. The linear photon-energy dependent dielectric functions and some optical properties such as the refractive index, energy-loss function and reflectivity are calculated for both crystals within the scissor approximation. Moreover, some important optical parameters such as the effective number of valance electrons and the effective optical dielectric constant are calculated. We have also made some comparisons with related experimental and theoretical data which is available. It is found that the method used estimated the properties of these crystals quite well.