IUVSTA 15th International Vacuum Congress (IVC-15), AVS 48th International Symposium (AVS-48), 11th International Conference on Solid Surfaces (ICSS-11)
    Surface Science Monday Sessions
       Session SS2-MoA

Paper SS2-MoA4
Molecular Adsorbate Geometries and Bondlengths on NiO(100); A Failure of Current DFT Theories

Monday, October 29, 2001, 3:00 pm, Room 121

Session: Molecular Interactions with Oxide Surfaces
Presenter: M. Kittel, Fritz-Haber-Institut der MPG, Germany
Authors: M. Kittel, Fritz-Haber-Institut der MPG, Germany
J.-T. Hoeft, Fritz-Haber-Institut der MPG, Germany
M. Polcik, Fritz-Haber-Institut der MPG, Germany
R.L. Toomes, University of Warwick, UK
J.-H. Kang, University of Warwick, UK
M. Pascal, University of Huddersfield, UK
C.L.A. Lamont, University of Huddersfield, UK
D.P. Woodruff, University of Warwick, UK
Correspondent: Click to Email
Current density-functional theory has been shown to be extremely successful in reproducing the local geometries and bondlengths of adsorbates on metal surfaces, for which there is a significant body of experimental data. In the case of oxide surfaces, however, there is a dearth of experimental structural data to compare with the results of such theory. Here we present the results of quantitative structure determinations for new studies of CO and NH@sub3@ on NiO(100) epitaxial films using photoelectron diffraction in the scanned-energy mode (PhD) combined with full multiple scattering simulations. Both species, like NO which we studied previously, occupy sites atop surface Ni atoms, with bondlengths which are slightly longer than we have found for the same species on metallic Ni surfaces, but much shorter (by up to 0.79 Å) than predicted by theory. The results highlight a major failure of current theory to provide an adequate description of molecule/oxide bonding, which was previously only evident through a comparison of experimental thermal desorption data with theoretical bonding energies. A comparison of the molecule-Ni nearest neighbour bondlengths for these singly-coordinated sites on NiO(100) with those found on metallic Ni(111) shows that while the bondlengths on the oxide surface are systematically longer than on the metal surface, these effects are far more subtle than those reflected by current theoretical treatments.