ATOMISTIC STRUCTURE OF STEPPED SURFACES

Atomistic computer simulation with embedded atom method (EAM) interato mic Forces was used to study the structure of surface steps on the {11 1} unreconstructed surface in fee metallic materials. The energetics a nd local atomic relaxation behavior of ledges parallel to the [110] di rection were studied using a potential describing lattice properties o f Au. The vacancy formation energies in the stepped surfaces was also studied, and it was found that the energy of formation of a vacancy in a terrace is the same as that in the perfect unstepped surface. This value is 30% lower than that of the bulk. The vacancy formation energy in the ledge is reduced by a factor of two with respect to that of th e terraces. The structure of the ''up ledge'' (A step) is different fr om the ''down ledge'' (B step). These differences do not significantly affect the energy of the ledges, although they do affect the vacancy formation energies in sites in the second surface layer near the ledge . The implications of the results for the formation of kinks and the g eneral structure of high index surfaces are discussed.