The electronic structures and optical properties of BaTiO3 and SrTiO3 using first-principles calculations

The electronic-energy band structures and total density of states (TDOS) for bulk BaTiO3 and SrTiO3 were calculated by the first-principles calculations using density-functional theory and local-density approximation. The calculated band structure of BaTiO3 and SrTiO3 show the energy band gaps of 1.81 and 1.92 eV at the Γ point in the Brillouin zone, respectively. The optical properties of the both perovskites in the core-level spectra are investigated by the first principles under scissor approximation. The optical constants like refractive index and extinction coefficient of both BaTiO3 and SrTiO3 were derived from the calculated real and imaginary parts of the dielectric function. The calculated spectra were compared with the experimental results for BaTiO3, SrTiO3 in good agreement.