1. Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, United States
2. Department of Inorganic Chemistry, Fritz-Haber-Institute of the Max-Planck-Society, Berlin 14195, Germany
3. Department of Heterogeneous Reactions, Max-Planck-Institute for Chemical Energy Conversion, Mülheim an der Ruhr 45470, Germany
4. Consiglio Nazionale delle Ricerche, Istituto Officina dei Materiali, Trieste 34136, Italy