Diffusion dynamics of small two-dimensional atomic clusters Cu n (with n ranging from 1 to 8) on Cu(111) surface have been studied using molecular dynamics in the temperature range from 300 to 800 K. The diffusion coefficients of these clusters are derived from mean square displacement of cluster's mass-center, which is obtained by long simulation times (∼0.1 µs) and tracing of surface interstitial atoms. A drop in the diffusion migration energy for tetramer compared to the trimer or pentamer is found, and the migration energy for octamer is larger than that for the compact heptamer cluster. The diffusion prefactor of a heptamer is about 30 times larger than that for single atom diffusion. The characteristic temperature, derived from the Arrhenius plots, indicates that the heptamer starts to move at very low temperature (167 K).

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The diffusion dynamics of small two-dimensional atomic clusters Cux (1 x 8) on Cu(111) surface were studied using the molecular dynamics simulations and a modified analytic embedded-atom method in the temperature range from 200 K to 800 K. The cluster size and temperature dependence of the diffusion coefficients and migration energies are presented. Our simulations show that the diffusion migration energy of the Cu7 cluster is the highest and the prefactor for the Cu7 cluster is almost three orders of magnitude larger than that for single atom diffusion. This conclusion is consistent with the experimental results for similar metals. In addition, the dependence of cluster diffusion on film growth is also discussed.