We report density functional theory (DFT) calculations for gold atoms and dimers on the surface of graphene. The calculations were performed using the plane wave pseudopotential method. Calculations were performed for a variety of geometries, and both the graphene surface and gold atoms were allowed to fully relax. In agreement with experiment, our results show that the gold-gold interaction is considerably stronger than the gold-graphene interaction, implying that uniform coverage could not be attained. The minimum energy configuration for a single gold atom is found to be directly above a carbon atom, while for the dimer it is perpendicular to the surface and directly above a carbon-carbon bond. Our results are consistent with previous similar calculations.

We report first principles calculations of the geometry and electronic structure of 13 atom clusters of boron, aluminium, gallium and indium. These density functional theory calculations support the jellium model in the energy levels and molecular orbitals of the cluster and enable us to discuss the relevance of the superatom concept. We go on to examine a number of cluster symmetries in detail as a function of charge and comment on the successes and limitations of the jellium and superatom models in describing these clusters. In particular we find that the monovalent anionic cluster is the most stable and has the most symmetric structure. As charge changes the symmetry of the clusters decreases in a way that is dependent on symmetry and charge, but not atomic species.