Density functional calculations were made of the structural and dynamic properties of small Cu clusters (Cun, with n between 2 and 5) which were adsorbed on MgO(100). Because the Cu-Cu intracluster interactions were stronger than the cluster-surface interactions, the most stable geometries were similar to those in the gas phase; with the cluster in an upright position with respect to the surface. First-principles molecular dynamics simulations indicated that the adsorbed clusters diffused by means of so-called rolling and twisting motions; with barriers to motion that could be smaller than that for hopping diffusion of a single adatom.

Structure and Dynamics of Small Metallic Clusters on an Insulating Metal-Oxide Surface: Copper on MgO(100). V.Musolino, A.Selloni, R.Car: Physical Review Letters, 1999, 83[16], 3242-5