Manning's diffusion kinetics formalism for random alloys was adapted so as to produce a 2-tiered diffusion kinetics formalism, for mixed ionic crystals, in which diffusion was mediated by bound vacancy pairs. Both NaCl and CsCl structures were considered. Diffusion correlation effects were described for a situation where there could be 2 types of monovalent cation and 2 types of monovalent anion which competed for the bound vacancy pair. It was assumed that the 2 types of cation were randomly distributed; as were the 2 types of anion. Tracer correlation factors were expressed, in closed form, in terms of the sub-lattice atomic vacancy pair-exchange frequencies, the relative compositions of atomic species and the geometrical correlation factor. The results were in good agreement with Monte Carlo simulation results. It was shown, for the ternary mixed system, how ratios of tracer diffusion coefficients could be analyzed so as to give tracer correlation factors explicitly.

I.V.Belova, G.E.Murch: Philosophical Magazine A, 1999, 79[11], 2681-90