Chemical interdiffusion was analysed in strongly ionic crystals, for diffusion couples AYm-BYm, where A and B had the same charge numbers. The exact sum rule given by Moleko and Allnatt was used, which relating the phenomenological coefficients for diffusion in the multi-component random alloy, via monovacancies. It was shown that the ratio of the intrinsic diffusivities could be expressed very simply in terms of the atom-vacancy exchange frequencies, without correlation terms. For the case of an immobile anion sub-lattice, and making use of a highly accurate diffusion kinetics theory, it was shown that the interdiffusivity was mainly proportional only to the off-diagonal phenomenological coefficient which related the 2 cations.

Analysis of Interdiffusion via Isolated Vacancies in Strongly Ionic Crystals. I.V.Belova, G.E.Murch: Philosophical Magazine, 2004, 84[21], 2139-46