Large-scale computer modelling of Li impurities in KTaO 3 and K 1–xLi xTa 1–yNb yO 3 perovskite solid solutions

Abstract

The magnitudes of off-center Li displacements and the relaxation energies related to reorientation of Li are calculated in ABO 3 perovskites using the semi-empirical Hartree-Fock-based method of the Intermediate Neglect of Differential Overlap (INDO). The spatial extent of a lattice relaxation around Li impurities and contributions from different neighbours to the relaxation energy are discussed. We have applied the INDO method for the study of interaction between Li impurities in KTaO 3. The Li-Li interaction energy as a function of the Li-Li distance and orientation are calculated, including the lattice relaxation around Li-Li impurities. According to our calculations, the Li-Li interaction energies are smaller and less long-range than those estimated from earlier shell model calculations. Lastly, we discuss theoretical modelling of KTaO 3 perovskites with a small amount of Li and simultaneously diluted by Nb (K 1–xLi xTa yNb 1–yO 3, KLTN).