Investigation of physical proporties of ABO3 type perovskites

Adequate description of properties of perovskites compounds and of the related solid solutions requires knowledge of the shape of the local adiabatic potential for the host and impurity atoms. We report here on cluster ab-initio calculations of the local adiabatic potential for the Ti and Nb atoms in BaTiO3, SrTiO3 and KNbO3. To find the local adiabatic potential for an atom sitting at a lattice site, one has to calculate the total crystal energy as a function of atomic displacement from the equilibrium position at the site, ?E(?), assuming the remaining atoms to occupy their equilibrium positions in the perovskite cubic lattice. The total energies and the one-electron cluster properties were calculated by the Hartree-Fock-Roothaan ab initio MO LCAO SCF formalism using the PC GAMESS version of the GAMESS (US) QC package. The correlation effects were taken into account within the Møller--Plescet perturbation theory method (MP2).