SELF-DIFFUSION MECHANISMS FOR ADATOMS ON FCC(100) SURFACES

We investigate the mechanisms and associated energetics of diffusion for the Ni/Ni(100), Cu/Cu(100), Pd/Pd(100) and Ag/Ag(100) systems using the corrected effective medium method. The Ni/Ni(100) and Cu/Cu(100) systems are shown to favor the atomic-exchange diffusion mechanism whereas the Pd/Pd(100) and Ag/Ag(100) systems favor the bridge-hopping diffusion mechanism. The explicit inclusion of the kinetic-exchange-correlation energy is critical to determination of the favored mechanism. A simple model, based upon binding ''curves'' from dimer and bulk binding, is developed to provide a physical explanation of the different behavior exhibited by the various metal systems.