Cluster diffusion on a surface has been simulated with a triangular-lattice-gas model and the kinetic Monte Carlo method. The dependence with temperature and cluster size and the detailed mechanisms of cluster motion have been studied, as well as the role of impurities. Results show that cluster motion occurs through a mechanism in which random atomic displacements along the cluster perimeter make it deform and crawl. In contrast, evaporation-condensation has a negligible role at low temperatures. If impurities with a lower binding energy are added, they concentrate at the cluster perimeter and greatly facilitate cluster motion by lowering activation energies, provided that atom-impurity exchanges are possible.

• Received 12 April 1994

DOI:https://doi.org/10.1103/PhysRevB.50.5578