The surface diffusion of Cu adatoms in the presence of an adisland at face-centered cubic or hexagonal close-packed sites on Cu(111) was studied using the embedded atom model potential derived by Mishin et al.  The diffusion rates along straight (with close-packed edges) steps with (100) and (111)-type microfacets (respectively, step A and step B) were first investigated using the transition state theory in the harmonic approximation. It was found that the classical limit beyond which the diffusion rates follow an Arrhenius law was reached above the Debye temperature. The Vineyard attempt frequencies and the (static) energy barriers were reported. Then a comparison was made with the results of more realistic classical molecular dynamic simulations which also exhibit an Arrhenius-type behavior. It was concluded that the corresponding energy barriers were completely consistent with the static ones within the statistical errors and that the diffusion barrier along step B was significantly larger than along step A. In contrast the pre-factors were very different from the Vineyard frequencies. They increase with the static energy barrier in agreement with the Meyer-Neldel compensation rule and this increase was well approximated by the law proposed by Boisvert et al. As a consequence, the remaining part of this work was devoted to the determination of static energy barriers for a large number of diffusion events that could occur in the presence of an adisland. In particular, it was found that the corner crossing diffusion process for triangular adislands was markedly different for the two types of borders (A or B). From this set of results the diffusion rates of the most important atomic displacements could be predicted and used as input in kinetic Monte Carlo simulations.

Diffusion Rates of Cu Adatoms on Cu(111) in the Presence of an Ad-Island Nucleated at FCC or HCP Sites. M.C.Marinica, C.Barreteau, D.Spanjaard, M.C.Desjonquères: Physical Review B, 2005, 72[11], 115402 (16pp)