Structure and diffusion of clusters on Ni surfaces

Abstract

The optimal structure of Ni clusters on Ni(100) and Ni(111) and Pt clusters on Ni(100) are studied using the embedded atom method (EAM). Unlike Ni and Pt clusters on Pt(100) [1,2], the clusters always preferred relatively closed-packed islands over linear chains. The structure of Ni clusters on Ni(111) were generally similar to those of Ir on Ir(111) [3]. Significant variations in dissociation energy indicate that certain “magic number” cluster sizes are favored over others. The diffusion mechanisms of the small clusters were investigated to determine the optimal migration paths and corresponding migration energies. The energy barriers for small clusters of Ni on Ni(100) are comparable to monomers, in qualitative agreement with recent FIM experiments for Pt x /Pt(100) [4]. For Ni x /Ni(111) migration energies generally increased with increasing cluster size, in qualitative agreement with experimental results for Ir clusters on Ir(111) [3].