Covalent bonding of sulfur on Ni(001): S as a prototypical adsorbate catalytic poisoner

The effects of sulfur, as a prototypical catalytic ‘‘poisoner,’’ on the structural, electronic, and magnetic properties of Ni(001) are investigated with the highly precise full-potential linearzed augmented-plane-wave method. The Si-Ni interlayer distance is determined to be 1.36 Å. The poisoning is found to be caused by local Ni-S covalent-bond formation and the ‘‘lone-pair’’ density polarization on the S site. A nearly magnetically dead Ni surface layer (0.12${\mu }_B$) is obtained. The indirect long-range (screening) interaction is manifested in a layer-dependent oscillatory on-site charge transfer between $e_g$ and $t_{2g}$ symmetry states for Ni inner layers.