Ab initio calculations of Born charges in ferroelectrics with a perovskite structure

A method has been proposed for calculating Born effective charges in compounds with a cubic perovskite structure. The method is based on the first-principles calculation of individual contributions from the short-range interaction and the intercell dipole-dipole interaction to the Born tensor Z (ii) (s) for crystalline dielectrics. It has been shown that the contribution from the short-range interaction Z (ii) (sr) (s) to the Born tensor components can be derived from ab initio calculations performed for polyatomic clusters. The results of the calculations of the short-range interactions Z (ii) (sr) (s) for the cubic phases of the BaTiO3, SrTiO3, CaTiO3, PbTiO3, BaZrO3, PbZrO3, KNbO3, and KTaO3 compounds with the use of the electronic structure calculations within the Hartree-Fock approximation and the density functional theory are presented. For the BaTiO3, SrTiO3, CaTiO3, PbTiO3, KNbO3, and KTaO3 compounds, the components of the complete Born tensor have been also calculated. The obtained values of Z (ii) (s) are in good agreement with the results of the calculations in terms of the linear response theory and the Berry phase approach.