A model for a long-range ordered alloy was considered in which the sub-lattices were assumed to exist  a priori. This was a natural extension of the ordered state of the well-known random alloy model. The analysis which was developed was a modification of the Mannings ordered model for the random alloy, with emphasis being placed on the percolative aspects. It was shown that the percolation threshold for the mobile component in the highly-ordered alloy moved from a composition given by 1-f (where f was the tracer correlation factor in the lattice of a pure component - the random alloy result) to a composition that was given by 1-½f. Expressions were also derived for the average jump frequencies. These, together with a previous analysis of tracer correlation, permitted the tracer diffusion coefficients to be predicted.

I.V.Belova, G.E.Murch: Philosophical Magazine A, 1996, 73[4], 1223-35