A detailed molecular-dynamics study was made of the diffusion and coalescence of large (249-atom) gold clusters on graphite surfaces. The diffusivity of clusters was found to be comparable to that for single adatoms. Likewise, and even more important, cluster dimers were also found to diffuse at a rate that was comparable to that for adatoms and single clusters. As a consequence, large islands formed by cluster aggregation were also expected to be mobile. Using kinetic Monte Carlo simulations, and assuming a proper scaling law for the dependence on size of the diffusivity of large clusters, it was found that islands consisting of as many as 100 clusters should exhibit significant mobility. This result has profound implications for the morphology of cluster-assembled materials.

Diffusion of Gold Nanoclusters on Graphite. Lewis, L.J., Jensen, P., Combe, N., Barrat, J.L.: Physical Review B, 2000, 61[23], 16084-90