C and S induce changes in the electronic and geometric structure of Pd(533) andPd(320)

Abstract

We have performed ab initio electronic structure calculations of C and S adsorption on twovicinal surfaces of Pd with different terrace geometries and widths. We find that bothadsorbates induce a significant perturbation of the surface electronic and geometricstructure of Pd(533) and Pd(320). In particular, C adsorbed at the bridge site at the edgeof a Pd chain in Pd(320) is found to penetrate the surface to form a sub-surface structure.The adsorption energies show an almost linear dependence on the number ofadsorbate–metal bonds, and lie in the ranges 5.31–8.58 eV for C and 2.89–5.40 eV for S. Astrong hybridization between adsorbate and surface electronic states causes alarge splitting of the bands, leading to a drastic decrease in the local densities ofelectronic states at the Fermi level for Pd surface atoms neighbouring the adsorbate,which may poison catalytic activity of the surface. Comparison of the results forPd(533) with those obtained earlier for Pd(211) suggests a local character of theimpact of the adsorbate on the geometric and electronic structures of Pd surfaces.