Metal Surface Diffusion Kinetics Of Adsorption Clusters

In this paper,we have studied the diffusion of trimer and hexamer on Pt(111) surface,the atomic interaction is modeled by the embedded-atom method potential. From the molecular dynamics simulation,two processes for the diffusion of trimer are observed,they are concerted translation and rotation,in which the cluster always keeps as a compact triangle.The diffusion processes of hexamer,however,are much complicated and richer than those of the trimer.Besides the processes such as single-atom hopping,two-atom shearing and six-atom concerted translation,the exchange is also observed.Comparing with the diffusions on Cu(111) surface,which are simulated with the Rosato-Guillopé-Legrand potential,some interesting characteristics are found for the diffusions of trimer and hexamer on Pt(111) surface. For example,the hopping of single atom and the shearing of two atoms of hexamer are always along the B-step edge of the cluster,while the exchange always occurs in the surface row near the A-step edge,and the preference path of the concerted translation of hexamer on Pt(111) surface is far different from that on Cu(111) surface.