Diffusion of gold nanoclusters on graphite

We present a detailed molecular-dynamics study of the diffusion and coalesc ence of large (249-atom) gold clusters on graphite surfaces. The diffusivit y of clusters is found to be comparable to that fur single adatoms. Likewis e, and even more important, cluster dimers are also found to diffuse at a r ate that is comparable to that for adatoms and singleclusters. As a consequ ence, large islands formed by cluster aggregation are also expected to be m obile. Using kinetic Monte Carlo simulations, and assuming a proper scaling law for the dependence on size of the diffusivity of large clusters, we fi nd that islands consisting of as many as 100 clusters should exhibit signif icant mobility. This result has profound implications for the morphology of cluster-assembled materials.