Electronic structure studies of adsorbate-induced surface reconstructions: oxygen on Rh(1 0 0)

Solid-state Fenske–Hall band structure calculations have been used to study the electronic structure and bonding that occur on an “asymmetric” clock reconstructed Rh(1 0 0) surface with a half-monolayer of O atom adsorbates. The displacement of the top-layer Rh atoms on reconstructed O/Rh(1 0 0) is similar to that observed when a half-monolayer of C or N atoms adsorb onto clean Ni(1 0 0). Unlike the five-coordinate C or N adsorbates that adsorb into effectively coplanar sites on the Ni(1 0 0) surface, however, O atoms sit well above the Rh surface plane and occupy three-coordinate adsorption sites. The results of these calculations show that the asymmetric clock reconstruction of O/Rh(1 0 0) increases the negative charge localized on the highly electronegative O atoms and strengthens the O–Rh bonding relative to an unreconstructed surface. This suggests that, in contrast to the C(N)/Ni(1 0 0) clock, which appears to be driven primarily by the restoration of metal–metal bonding, the asymmetric O/Rh(1 0 0) clock reconstruction is driven by the optimization of the O atom bonding environment. Comparisons of the O/Rh(1 0 0) and C(N, O)/Ni(1 0 0) surfaces further indicate that the electronegativity and electron count of the adsorbed species, as well as the electron count and physical size of the metal, all play a role in determining the preferred atomic geometries of these adsorbate-covered transition metal surfaces.