Point defects in ferroelectrics with perovskite structure

First-principle calculations of the geometry and electronic structure of lattice defects (substituents, vacancies, and binary complexes) in perovskites are considered. A supercell method and modifications of a cluster method for simulating point lattice defects in insulators are discussed. Experimental data on dielectric relaxation in magnesium- and manganese-doped strontium titanate and possible mechanisms of the formation of reorientable polar defects are considered.