Semi-empirical hartree-fock calculations for interacting Li impurities in KTaO3

Abstract

Equilibrium off-center displacements of two Li impurities substituting neighboring K sites in KTaO3, the relaxation pattern of O ions around the impurities and the Li-Li interaction energies in fixed and relaxed O surrounding have been calculated using the semi-empirical INDO method. The Li off-center displacement is 0.6 – 0.7 Å in all cases: the displacements of O nearest neighbors to Li are up to 0.06 Å, and the displacement of more distant atoms negligibly small, within the calculational accuracy. The Li-Li interaction energy is positive, revealing the deviations from the dipole-dipole interaction in a polarized crystal, and strongly enhanced due to the O relaxation.