A systematic microscopic approach to diffusion and diffusion-limited processes in Ni3Al was presented. These processes were identified as controlling deformation of this material under certain conditions. Embedded atom method calculations were performed using kinetic Monte Carlo and Dimer methods for finding saddle-points. The tracer diffusivities were predicted as functions of composition and temperature. The agreement with available experimental data was good. It was found that, below about 1000K, the diffusivity was a sensitive function of composition; exhibiting a marked dip on the Ni-rich side at 76at%Ni. This agreed well with experiment, although the latter showed that this structure appeared below about 1300K. It was shown that the structure arose from a composition- dependence of the vacancy formation energy and of the pre-exponential diffusivity parameter. The mobility of an antiphase boundary perpendicular to its plane was also calculated, and it was concluded that vacancy-assistance was very likely. It was concluded that the kinetic Monte Carlo plus Dimer method worked well for these problems at above 700K. It was less effective at lower temperatures, due to

the presence of short-range low-energy hops that tended to localize the vacancy and decreased the efficiency of the calculation.

Calculations of Diffusion and Diffusion-Limited Processes in Ni3Al using Accelerated Molecular Dynamics. Harris, C., Tedstrom, R., Daw, M.S., Mills, M.J.: Computational Materials Science, 2006, 37[4], 462-9