Wannier Functions and Chemical Bonding in Crystals with the Perovskite-Like Structure:SrTi0_3,BaTi0_3,PbTi0_3,and LaMn0_3

摘要

The electronic structure of the cubic perovskites SrTiO_3,BaTiO_3,PbTiO_3,and LaMnO_3 is calculated by Hartree-Fock and density functional theory methods in the approximation of linear combinations of atomic orbitals.The local properties of the electronic structure of these crystals (atomic charges,bond orders,atomic covalences,and total valences) are obtained using the minimal valence basis of Wannier-type atomic orbitals (WTAOs).WTAOs are defined as the mostly localized atomic-like Wannier functions generated from the Bloch states,corresponding to some occupied and vacant bands.WTAOs are constructed by means of a variational procedure suggested earlier.The atomic charges obtained via WTAO technique are compared to the traditional Mulliken atomic charges.The results of the population analysis demonstrate the closeness of the local properties of cubic SrTiO_3,BaTiO_3,and PbTiO_3.The covalence appears to be essential for the nearest-neighbor oxygen-transition metal bond.