Interaction of silver adatoms and dimers with graphite surfaces

The energetics and surface relaxation of silver adatoms and dimers and carbon adatoms on graphite are investigated using an ab initio density functional theory description. The energy landscape sketched along [1 1 0] indicates that the sites favored by silver adatoms are near carbon β-sites, but the insignificant energy differences among binding sites means that atomic mobility on the graphite surface is very high. These results are consistent with the available experimental data from scanning tunneling microscopy. The energy difference between binding sites for silver dimers is found to be even smaller than that for adatoms, indicating high surface mobility for dimers as well as atoms. The deformation of graphite surfaces by silver adatoms is small and limited to those adjacent carbon atoms in the top layer. The preferred carbon adatom binding site is over a carbon–carbon bond. Larger surface deformations result from carbon adatoms on the graphite surface. The effect of different variables, such as the number of layers in the slab, supercell size and the size of the basis set, were also examined and these results are included.