Previously developed computational techniques and results were used to study the atomic mechanisms of tracer self-diffusion. Calculations were made of the activation energies for Ni and Al self-diffusion, via 3 possible atomic mechanisms, in perfectly stoichiometric material. These diffusion mechanisms involved next-nearest neighbor vacancy jumping, a 6-jump vacancy mechanism or a 4-ring mechanism. The results of the simulations indicated that self-diffusion in stoichiometric NiAl was dominated by the next-nearest neighbor vacancy jump mechanism. It was suggested that the diffusion of Al via this mechanism was likely to occur more slowly, and with a higher activation energy, than did the diffusion of Ni. The 6-jump mechanism was found to be less favorable, but was still highly competitive when compared with the next-nearest neighbor vacancy mechanism. The 4-ring mechanism was the least efficient, for both Ni and Al diffusion.

Y.Mishin, D.Farkas: Philosophical Magazine A, 1997, 75[1], 187-99