Modeling of defects and surfaces in perovskite ferroelectrics

The ab initio linear muffin-tin orbital method combined with density functional theory (local approximation) and the semiempirical method of the intermediate neglect of differential overlap (INDO) based on the Hartree-Fock formalism are used for the study of the F centers and the hole polarons in KNbO₃ perovskite crystals. We present and discuss results of the calculations for SrTiO₃ (1 0 0) surface relaxation with different terminations (SrO and TiO₂) using an ab initio methods based on Hartree-Fock (HF) and density functional theory (DFT) formalisms. We compare our results with previous ab initio and shell model (SM) calculations and LEED experiments.