A systematic density functional study was made of the adsorption of copper, silver, and gold adatoms on pristine graphene, especially accounting for van der Waals (vdW) interactions by the vdW-DF and PBE+D2 methods. The preferred adsorption site (among top, bridge and hollow) together with the corresponding distortion of the graphene sheet were analyzed and the diffusion paths were identified. Both vdW schemes showed that the coinage metal atoms do bind to the graphene sheet and that in some cases the buckling of the graphene layer could be significant. Only the results for silver were qualitatively at variance with those obtained with the generalized gradient approximation, which gives no binding in this case. However in all three cases, some quantitative differences were observed between the vdW-DF and PBE+D2 methods. For instance the adsorption energies calculated with the PBE+D2 method were systematically higher than the ones obtained with vdW-DF. Moreover, the equilibrium distances computed with PBE+D2 were shorter than those calculated with the vdW-DF method.

Adsorption of Cu, Ag, and Au Atoms on Graphene Including Van Der Waals Interactions. Amft, M., Lebègue, S., Eriksson, O., Skorodumova, N.V.: Journal of Physics - Condensed Matter, 2011, 23[39], 395001