The implications of vacancy-pair mechanisms for chemical diffusion in intermetallic B2-structured compounds were considered, with particular regard to the so-called triple-defect mechanism. It was shown that the vacancy-pair mechanism could not contribute to chemical diffusion in the intermetallic compound at the stoichiometric composition, AB. The triple-defect concept was extended to non-stoichiometric compositions by including isolated anti-structural atoms. By using Monte Carlo simulation, it was shown that the efficiency of the triple-defect mechanism, in mediating chemical diffusion, increased linearly with increasing anti-structural atom composition. However, the efficiency remained relatively low unless the composition was highly non-stoichiometric.

Chemical Diffusion by Vacancy Pairs in Intermetallic Compounds with the B2 Structure. G.E.Murch, I.V.Belova: Philosophical Magazine Letters, 2000, 80[8], 569-75