DFT investigation of lattice parameters, spontaneous polarization, and refractive indices of tetragonal BaTiO3 and PbTiO3

In the present work, we study the structural, electrical and optical properties of barium titanate (BaTiO3) and lead titanate (PbTiO3) using the plane wave pseudopotential method and the PBESOL approximation in the framework of density functional theory (DFT). We use the open-source program Quantum Espresso to perform the calculation of optimized lattice parameters, spontaneous polarization and refractive indices of tetragonal BaTiO3 and PbTiO3 single crystals. In the calculations, all types of pseudopotentials were considered: ultrasoft pseudopotentials (USPP), norm-conserving pseudopotentials (NCPP) and projector-augmented wave (PAW). The calculated values of the optimized lattice parameters, the spontaneous polarization and the refractive indices of the tetragonal BaTiO3 and PbTiO3 show a good agreement with the experimental values, especially for the USPP and PAW pseudopotentials.