Surface adsorbate diffusion was examined using a numerical algorithm which incorporates a kinetic treatment in conjunction with a time-dependent Monte Carlo formalism. Nearest- and next-nearest neighbor ad particle interactions were included. The method was based on a probabilistic description of ad particle jump events; and the diffusion rate was determined by the energetics of ad particle interactions on the lattice. In addition, the rare event problem associated with other theoretical treatments of diffusion was overcome by using a highly efficient algorithm. Consequently, it was possible to observe events, including ordering and island formation, which occurred on time scales which were longer by orders of magnitude than those for simple adsorbate diffusion. The initial investigations included that a variety of diffusion mechanisms may be operative depending on the ad particle interactions in the system. With nearest-neighbor interactions, the present systems achieve a random walk limit at long times. Also observed were ordering and island formation, as well as a change in diffusion mechanism, as next-nearest-neighbor attractive energies were increased.

Time-Dependent Monte Carlo Studies of Surface Diffusion. A.M.Bowler, E.S.Hood: The Journal of Chemical Physics, 1991, 94[7], 5162-71