Molecular orbital studies of ABO3perovskites by the SCF-MS-Xα method: local densities of states, chemical bonding and optical transitions

The evolution of electronic properties for the series of perovskite compounds BaTiO 3 , KNbO 3 and KTaO 3 is investigated through the SCF-MS-X alpha method applied to TiO 6 8- , NbO 6 7- and TaO 6 7- octahedral clusters. Local densities of states of d and p character are derived from X alpha ground states eigenvalues and compared with band energy results. Theoretical densities of states obtained when introducing photoionisation cross section effects are discussed in regard to XPS O 2p valence bands. Ionisation energies and optical transitions are calculated using the transition-state model and compared with XPS binding energies and experimental optical data, respectively. The spatial distributions of the molecular orbital and the characteristics of covalency deduced from a population analysis show slight variations along the series.