Crossover in the adsorption properties of alkali metals on graphene

摘要: The adsorption of alkali metals (AMs) on single layer graphene is studied using first principles methods. We observe a common trend in the binding distance, charge transfer, and work function $(W)$ at certain coverage AMs with increase proportion $\ensuremath{\rho}$ (adatom/C atom) covered by AM. A dip these properties occurs $\ensuremath{\rho}\ensuremath{\approx}0.04$ for all except Li, which it $\ensuremath{\rho}\ensuremath{\approx}0.08$. This behavior due to transition adsorbed from individual atoms two-dimensional metallic sheets that exert depolarization effect. $W$ exhibits asymmetric dependence $\ensuremath{\rho}$: adatom side but saturation side, contrast case bulk graphite.