Abstract: 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 $D\varpropto N^{-1.08\pm0.027}$.

Key words: cluster diffusion, Monte Carlo simulation, barrier