Computer simulation techniques were applied to these perovskite materials in order to clarify the mechanisms and energetics of O ion migration. A common set of interatomic potentials was derived, for these 4 compounds, which correctly reproduced their cubic structures. The results supported suggestions that their diffusion was mediated by O ion vacancies. An analysis of the potential energy surface demonstrated that vacancy migration took place along the anion octahedron edge, via a curved path rather than a straight one. The calculated migration energies ranged from 0.5 to 0.9eV, and were in accord with available experimental data. The relationship between the cation size and the migration energy was considered. It was investigated by modifying the interatomic potential function so as to relate the ionic radii directly to the short-range repulsive term. A study was also made of the energy of solution of an alkaline-earth dopant at the La site, with O vacancy compensation. It was found that ion size effects were important, with Sr being calculated to have the highest solubility.

M.Cherry, M.S.Islam, C.R.A.Catlow: Journal of Solid State Chemistry, 1995, 118[1], 125-32