An importance-sampling method was presented which, when combined with a Monte Carlo procedure for evaluating transition state theory rates, permitted computation of classically exact transition state theory surface diffusion constants at arbitrarily low temperatures. In the importance-sampling method, a weighting factor was applied to the transition state region, and Metropolis steps were chosen from a special distribution which facilitates transfer between the two important regions of configuration space: the binding site minimum and the saddle point between two binding sites. The method was applied to the diffusion of Rh on Rh(111) and of Rh on Rh(100), in the temperature range of existing field ion microscope experiments.

Surface Self-Diffusion Constants at Low Temperature: Monte Carlo Transition State Theory with Importance Sampling. A.F.Voter, J.D.Doll: The Journal of Chemical Physics, 1984, 80[11], 5814-7