Geometry and electronic structure of alumina-supported Ag clusters

PHYS 340

Elizabeth A. Sokol, esokol@sas.upenn.edu1, Sara E. Mason, samason@sas.upenn.edu1, Valentino R. Cooper, vcooper@physics.rutgers.edu2, and Andrew M. Rappe, rappe@sas.upenn.edu3. (1) The Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA 19104, (2) Dept. of Physics and Astronomy Condensed Matter Theory, Rutgers, The State University of N.J, 136 Frelinghuysen Road, Piscatawat, NJ 08854, (3) Makineni Theoretical Laboratories, Department of Chemistry, University of Pennsylvania, 231 South 34th Street, Philadelphia, PA 19104-6323
The geometry and electronic structure of 3- and 4-atom silver clusters on the (0001) alumina surface are explored by DFT-GGA. In all of the optimized geometries for cluster adsorption, two chemically distinguishable cluster-surface interactions are present. We find that the clusters form ionic bonds with surface oxygen and covalent bonds with surface aluminum. A consequence of these two simultaneous bonding interactions is that the supported silver clusters are dipolar. We also find that the cluster adsorption induces significant surface relaxation in the oxide due to the electrostatic interactions. We dicuss how the shape of the cluster, along with the geometry of the initial deposition onto the surface, determine the balance of formed ionic and covalent cluster-surface bonds. Finally, we demonstrate the chemical inequivalence of the silver atoms of the supported clusters through electronic structure and adsorption of different species on the supported clusters.
 

Fundamentals of Metal Oxide Catalysis
1:20 PM-4:40 PM, Wednesday, 13 September 2006 Grand Hyatt San Francisco -- Portrero, Oral

Division of Physical Chemistry

The 232nd ACS National Meeting, San Francisco, CA, September 10-14, 2006