It was recalled that tracer diffusion of Co and Ga in Co-Ga had previously been described primarily in terms of a triple-defect mechanism based upon a divacancy mechanism and the existence of triple-defect disorder. Using the interaction energies employed to describe the partitioning of the vacancies and atoms in Co-Ga by Waegemaekers and Van Ommen (1982), Monte Carlo simulations of the tracer diffusivities in Co-Ga were performed. Use was made of a general isolated vacancy diffusion model with nearest-neighbor jumps, and no explicit or implicit binding between the vacancies. The model was fully consistent with triple-defect disorder in Co-Ga. It was shown that the tracer diffusion data could be well described in Co-Ga without the need for the triple-defect mechanism. It was found that Ga performed the equivalent of a next-nearest neighbor jump by jumping via the Co sub-lattice where it had a very short residence time, whereas the triple-defect mechanism required a formal next-nearest neighbor jump for Ga. It was noted that tracer diffusion measurements alone could probably not resolve this difference.

A New Interpretation of Tracer Diffusion in Co-Ga. I.V.Belova, G.E.Murch: Philosophical Magazine A, 2001, 81[1], 95-108