Tailoring Li adsorption on graphene

The technological potential of functionalized graphene has recently stimulated considerable interest in the study of the adsorption of metal atoms on graphene. However, a complete understanding of the optimal adsorption pattern of metal atoms on a graphene substrate has not been easy because of atomic relaxations at the interface and the interaction between metal atoms. We present a partial particle swarm optimization technique that allows us to efficiently search for the equilibrium geometries of metal atoms adsorbed on a substrate as a function of adatom concentration. Using Li deposition on graphene as an example we show that, contrary to previous works, Li atoms prefer to cluster, forming four-atom islands, irrespective of their concentration. We further show that an external electric field applied vertically to the graphene surface or doping with boron can prevent this clustering, leading to the homogeneous growth of Li.