ALLOY FORMATION ENERGETICS AND DYNAMICS IN THE NI/CU(100) AND NI/CU(111) SYSTEMS

We investigate the diffusion, agglomeration, and alloy formation of Ni atoms and islands on Cu (100), Cu (111), and a stepped Cu (111) surface. Stochastic molecular dynamics simulations at constant temperatures are used in conjunction with the generation of all energies and forces from the semiempirical density functional based molecular-dynamics/Monte-Carlo corrected effective medium theory. At temperatures from 300 to 900 K, significant amounts of surface alloying occurs at step edges but not on terraces. The more favorable mechanism of alloy formation is for adatoms on the upper terrace to be incorporated near the step edge via displacement of the edge outwards. The alternative process of incorporation of an adatom on the lower terrace into the step is less favorable.