The self-diffusion coefficients for the mono-vacancy mechanism, as described in terms of the Arrhenius relationship, were calculated. Many-body interatomic potentials, based upon the embedded atom model, were used (together with the static relaxation method) to study the static and dynamic properties of vacancies. The defect formation and migration energies, their corresponding relaxation volumes, and vibrational entropies, were evaluated. Particular attention was paid to Ni diffusion in Ni3Al. The results of the present calculations suggested that simple vacancy-Ni interchange jumps (in ordered or disordered samples) were energetically more favorable than were correlated 6-jump cycles. Although an energy difference of 0.35eV favored migration via ordering jumps rather than disordering jumps, the entropy factors varied in the opposite manner; thus suggesting that both types of jump contributed to Ni diffusion. Disordering jumps could be neglected only at temperatures below 770K. In this case, a pre-exponential factor of 2 x 10-4m2/s was deduced.

Diffusion by Vacancy Mechanism in Ni, Al, and Ni3Al: Calculation Based on Many-Body Potentials. Debiaggi, S.B., Decorte, P.M., Monti, A.M.: Physica Status Solidi B, 1996, 195[1], 37-54