First-principles study of sulfur overlayers on Pd(111) surface

We present gradient corrected density functional theory investigations of the adsorption of sulfur on the Pd(I 11) surface for a wide range of coverages up to a monolayer (ML). Adsorption of atomic S on the fcc hollow sites is the most energetically favorable at low and medium coverages (<= 0.50 ML). Our studies suggest that at low coverages, island formation with a (root 3 x root 3) structure will occur in agreement with experimental observations. At S coverages above 0.50 ML, we find a tendency to form S-S bonds on the surface. Electronic density of states plots indicate that as S coverage increases, a weakening of the S-Pd interactions occurs which is compensated by enhancement of the S-S interactions. (c) 2005 Elsevier B.V. All rights reserved.