Coverage dependent self-diffusion on Cu(111) by molecular dynamics

We studied the coverage dependence of the self-diffusion on the Cu(111) sur face using molecular dynamics simulations. The adatoms coalesce to a large island whose migration energy increases with coverage, attaining 0.37 eV ab ove a concentration of 25%. The migration rate of the island's atoms scales with their number as N-1, while step atoms are fast diffusing independent of the cluster size. Detailed trajectory analysis revealed that cluster dif fusion occurs via 'step running' of the peripheral atoms that initiate conc erted movements of the inner cluster atoms. In addition, adatoms and vacanc ies are spontaneously created and annihilated on the island's terrace, cont ributing to the migration of the island. These findings describe the most i mportant processes of cluster diffusion involved in the early stages of gro wth on this surface. (C) 1999 Elsevier Science B.V. All rights reserved.