The point defect structure of this material was investigated by using atomistic computer simulations. A set of short-range potential parameters was derived by using an empirical fitting procedure. These parameters were then incorporated into a shell model. A 2-region strategy was used in combination with the Mott-Littleton method for defect calculations. Intrinsic defects, Frenkel- and Schottky-type disorder, polarons, and reduction/oxidation mechanisms were treated, as well as many extrinsic defects. The manner in which these ions were introduced into the crystal, their agglomeration into defect complexes, and their possible off-center displacements were studied. It was found that intrinsic disorder was of minor importance, and that small electron polarons were possibly stable. The calculations supported the idea that reduction was significantly affected by pre-existing O vacancies which resulted from the charge compensation of accidental acceptor impurities. Extrinsic monovalent ions substituted at the K sites, for which no charge compensation was necessary. Ions of other valencies were incorporated at both cation lattice sites. This then gave rise to charge self-compensation which, in some cases, was combined with the formation of O vacancies.

M.Exner, H.Donnerberg, C.R.A.Catlow, O.F.Schirmer: Physical Review B, 1995, 52[6], 3930-40