Molecular Adsorption Bond Lengths At Metal Oxide Surfaces: Failure Of Current Theoretical Methods

New experimental structure determinations for molecular adsorbates on NiO(100) reveal much shorter Ni-C and Ni-N bond lengths for adsorbed CO and NH3 as well as NO (2.07, 1.88, 2.07 Angstrom) than previously computed theoretical values, with discrepancies up to 0.79 Angstrom, highlighting a major weakness of current theoretical descriptions of oxide-molecule bonding. Comparisons with experimentally determined bond lengths of the same species adsorbed atop Ni on metallic Ni(111) show values on the oxide surface that are consistently larger (0.1-0.3 Angstrom) than on the metal, indicating somewhat weaker bonding.