Structures and stabilities of small Co clusters on a Cu(111) surface: A theoretical study

Structures and relative stabilities of small Con clusters (n = 1-12) on a Cu(111) surface are studied using molecular dynamics simulations. It is shown that the supported clusters are all in two-dimensional island structures of the edges forming square microfacets (A step) and/or triangular microfacets (B step) with the substrate. For non-magic-number clusters, the lowest energy structures are the ones of the edges with more A steps and the most unstable structures are the ones of the edges with only A steps or B steps due to the lattice mismatch of the Con/Cu(111) system. Magic number clusters are truncated triangular or elongated shapes with a closed atomic shell and maximum nearest-neighbor bonds. In addition, the anomalous mobility is found for Co3 and Co6 clusters in the diffusion processes of these clusters. The concerted translation and rotation movements are responsible for their special diffusion behaviors.