COMPLICATED EXCHANGE-MEDIATED DIFFUSION MECHANISMS IN AND ON A CU(100) SUBSTRATE AT HIGH-TEMPERATURES

We present results obtained from a molecular dynamics study of the beh avior of isolated copper atoms placed on a copper substrate. The atomi c interactions are modeled by the embedded atom method. At 900 K we fi nd that diffusion frequently proceeds by a two-step exchange-mediated process. In the first step of the process an isolated surface atom ent ers the Cu(100) substrate creating a strain along a close-packed row. In the second step the strain is relieved by an atom in the strained r ow returning to the surface of the Cu(100) substrate. The atom which r eturns to the surface may be several atoms removed from the atom which entered the substrate.