The diffusion coefficient of vacancies which migrated in a B2 compound via 6-jump cycles was calculated by using rate equations. The latter was more general than the mean first-passage time concept. It was shown that the 2 methods yielded very similar results for typical measuring temperatures. The ratio of the probabilities of effective jumps, via (110) or (100) cycles, was determined by using the elementary properties of stochastic processes. The advantage of the present calculation was that no artificial restrictions on the parameters of the 6-jump cycles were required. It was shown that, for such general 6-jump cycles, no limits on the above probability ratio could be established. Measurements of this ratio therefore could not be used to deduce whether diffusion via 6-jump cycles was relevant in a specific material. The limits on the ratio of the tracer diffusion coefficients of the 2 constituents of the compound were also reconsidered. Analogous results were obtained for the correlated 3-jump cycles.

The Six-Jump Diffusion Cycles in B2 Compounds Revisited. R.Drautz, M.Fähnle: Acta Materialia, 1999, 47[8], 2437-47