Self-diffusion behaviors of two-dimensional compact hexagonal Cu7 and Pt7 clusters on the (111) surface were studied with molecular dynamics simulation. The diffusion barrier and pre-factor (D0) were determined from the Arrhenius diagram and compared with low-temperature field ion microscopy experiment. It was found that D0 for Pt7 clusters was about 35 times larger than that for Cu7 clusters. From the calculated phonon spectral densities of adatoms, it was deduced that the different diffusion behaviors of the two clusters might result from strong interactions between the Pt adatoms and surface atoms, which made the non-equivalent self-diffusion processes, which could produce a high pre-factor, occurred more easily for Pt7 cluster.

Comparative Study of Compact Hexagonal Cluster Self-Diffusion on Cu(111) and Pt(111). Yang, J., Hu, W., Xu, M.: Applied Surface Science, 2008, 255[5], 1736-40