We present Monte Carlo simulations and scaling theories for the size and temperature dependence of the diffusion coefficients of clusters of atoms and vacancies on surfaces. The mechanisms and rate-determining steps are found for a realistic model of the Xe/Pt(111) system. The coarsening of ensembles of clusters is also considered. By explicitly deriving the coarsening exponents, we show that the coarsening rate for systems dominated by coalescence due to cluster diffusion differs from the rates seen for Ostwald ripening.

• Received 8 June 1995

DOI:https://doi.org/10.1103/PhysRevLett.75.3158