Theoretical insight in the energetics of Co adsorption on a reconstructed Au(111) substrate

By means of tight-binding quenched-molecular-dynamics simulations, we have investigated the adsorption of a Co impurity on the reconstructed Au(111)-(22x root3) surface. The possible sites for nucleation on the Au inhomogeneous substrate have been identified and hierarchized in energy. Apart from the pure fee and hcp sites on the homogeneous part of the substrate, the adatom experiences Less pronounced minima in the pseudoternary sites on the sides of the discommensuration lines. Surprisingly, the stablest position is reached at the apparently low coordinated bridge site on top of the defect lines. We show that this can be understood from both relaxation and segregation effects.