Calculations were made of the loss in electrostatic and covalent energy which occurred when an O2- ion was removed from the apical or plane position. The Sr2+ ions were assumed to replace La3+ ions randomly. The electrostatic energy at an O position was calculated for each configuration of its nearest La,Sr ions, and the rest of the ions were taken into account by making self-consistent calculations of the average Madelung potential. The covalent energy was incorporated by means of a simple expression which fitted the dependence of the energy to the number of holes. Qualitative agreement was found with the observed dependence of the total number of vacancies upon the Sr content.

A.A.Aligia, S.Koval, R.Migoni: Solid State Communications, 1995, 95[1], 21-4