It was noted that, in recent observations of the Brownian motion of islands of adsorbed atoms and vacancies with a mean radius of R, the cluster diffusion constant had been observed to vary as R-1 and R-2. By performing a theoretical Langevin analysis of the cluster’s step-like boundary, cases of R-1, R-2 and R-3 were found; which corresponded to the 3 microscopic surface mass transport mechanisms of straight steps. A unified treatment was presented for the dynamics of steps and of clusters, and this was checked by carrying out Monte Carlo simulations of simple lattice gases.

S.V.Khare, N.C.Bartelt, T.L.Einstein: Physical Review Letters, 1995, 75[11], 2148-51