Sulfur-Induced Reconstruction of Ag(111) Surfaces Studied by DFT

Abstract

Density functional theory has been used to investigate the adsorption of sulfur atoms in the (Raiz(7)x Raiz(7)R19.1° unit cell of Ag(111). For the coverages Theta = 1/7 and 2/7 the S atoms adsorb at fcc and hcp hollow sites with negligible reconstruction of the surface. For Theta = 3/7 a large surface reconstruction occurs. The three Ag atoms around the hcp site that hosts a S atom move vertically and in-plane away from the hollow center provoking two effects: (i) the S atom adsorbed at this site penetrates under thesurface and (ii) a top site hosting the third S atom is transformedinto a new 3-fold hollow site. A detailed analysis of the differentcontributions to the adsorption energy shows that the energy cost of deforming the lattice is paid off by the stronger and morefavorable bonding of these two S atoms. This picture is confirmed by the new charge distribution after the reconstruction.