Adsorption and diffusion of Rh and Au dimers and trimers on graphene/Ru(0001)

Periodic density functional theory (DFT) calculations have been performed to study metal nanoparticles on graphene/Ru(0001). Specifically, we examined adsorption and diffusion of monomers, dimers, and trimers of Rh and Au on graphene/Ru(0001). These two metal species were chosen for their distinct behaviors in cluster formation on the graphene/Ru(0001) moiré. The fcc region of this surface was predicted to be where the nucleation of metal nanoclusters occurs. The diffusion mechanisms and energy barriers for metal dimers and trimers were calculated. It was shown that the mobility of Rh clusters decreases with the increase of cluster size. For Au, however, dimers and trimers diffuse faster than monomers on the moiré surface. These calculations give insights into the nucleation process of metal clusters on the graphene moiré.