First-principles study of sulfur overlayers on Pd(1 1 1) surface

We present gradient corrected density functional theory investigations of the adsorption of sulfur on the Pd(1 1 1) 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 (√3 × √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.