Monte Carlo simulation of the effect of atomic diagonal transition on cluster diffusion

The effect of atomic diagonal transition on the cluster diffusion and its size dependence is simulated by kinetic Monte Carlo method. The thresholds of atomic diagonal transition barriers E_dt are found to be 0.2eV and 0.4eV, corresponding to with and without evaporation and condensation mechanism, respectively. The results indicate that the cluster diffusion is controlled primarily by the atomic diagonal transition, and the cluster diffusion coefficient D decreases drastically with increasing E_d when E_d<E_dt. Moreover, D is also found to depend on the cluster size N. The size dependence of D can be described by D \varpropto N^-1:57\pm0:034 when E_d=0. This behaviour is very close to that of the perfect periphery diffusion. On the contrary, D is almost independent of E_d when E_d > E_dt, and the relationship between D and N changes into D\varpropto N^-1.08\pm0.027.