A dynamic smart Monte Carlo algorithm was introduced and its applicability to simulating the rare-event dynamics of adsorbate diffusion was assessed. Using the dynamical smart Monte Carlo method, the self-diffusion of an adatom in the Cu/Cu(001) and Rh/Rh(111) systems was simulated and the simulated diffusion coefficients were compared with values arising from molecular dynamics and transition-state theory. It was found that the accuracy of smart Monte Carlo was sensitive to details of the potential-energy surface. For Cu/Cu(001), the agreement between dynamical Smart Monte Carlo, molecular dynamics, and transition-state theory was excellent. A similar comparison for the Rh/Rh(111) systems showed discrepancies between these three techniques. It was found that the origins of the discrepancies in the Rh/Rh(111) system were transition-state re-crossings, for small simulation time steps, and low escape rates of the adatom from the binding sites, at large time steps. The sampling and dynamics in trajectories using a smaller time step for motion perpendicular to the surface than that for parallel motion were examined. These studies showed that low smart Monte Carlo escape rates in the Rh/Rh(111) system could be correlated with excessive sampling, beyond the configurational space of the potential-energy minimum, at large time steps. Re-crossings could be understood to arise from the absence of velocity correlations in the low-friction, transition-state region and could be minimized through the use of a large time step for parallel motion. With the appropriate choice of simulation time steps it was possible to improve the agreement between dynamical Smart Monte Carlo and more rigorous dynamical techniques.

Smart Monte Carlo for Accurate Simulation of Rare-Event Dynamics: Diffusion of Adsorbed Species on Solid Surfaces. P.V.Kumar, J.S.Raut, S.J.Warakomski, K.A.Fichthorn: Journal of Chemical Physics, 1996, 105[2], 686-95