Investigating energetics of Au8 on graphene/Ru(0001) using a genetic algorithm and density functional theory

Gold nanoparticles have been extensively studied for their catalytic activity both theoretically and experimentally. The moiré pattern formed by graphene supported on single crystal substrates creates a useful environment where the properties of Au nanoclusters can be studied, provided the structure and evolution of these clusters can be controlled. We used a genetic algorithm combined with DFT calculations to predict the lowest energy structures of a Au8 cluster on graphene/Ru(0001). The most stable cluster forms a double-layer Au wall structure for Au8 in the fcc region of the moiré pattern, where the Au8 cluster is most strongly adsorbed. Further calculations give estimates for the net diffusion barrier of Au8 as an intact cluster on the surface. Our results are consistent with the Au island structure experimentally observed on graphene/Ru(0001), and support the hypothesis that Au clusters aggregate through Oswald ripening with Au dimers being the most important diffusing species.