The interaction of transition metals belonging to the group Pt-Pd-Ni and the period Ni-Cu-Zn, with an Fs center of the MgO (100) surface was investigated using density functional theory. This study was aimed at finding the effect of the electron delocalization of an MgO oxygen vacancy on the interaction energies of the metals with the defect and the electronic configuration of the adsorbed metal atom. The degree of electron delocalization was determined from the maximum values of the electron localization function (ELF). It was confirmed that there were two electrons largely localized in the

center of the Fs vacancy. These electrons could delocalize over an adsorbed metal atom. This was the reason for the stabilization of some surface complexes. The MO analysis showed that the filling and the symmetry of the last occupied orbitals of the complex M-Fs/MgO depended on the kind of metal. In the case of Ni and Pt the orbitals from HOMO until HOMO-4 were d orbitals and the interaction orbital was the HOMO-5, while for Pd the interaction orbital was the HOMO and the orbitals HOMO-1 until HOMO-5 were of d character. This information was very useful for the study of the interaction of a H atom with del metal-Fs/MgO complex. The O vacancy modifies the interaction of a H atom with a metal deposited on the defect site due to changes in the electronic configuration of the metal. Therefore, the chemical activity of the metal strongly depended on the interaction metal support.

Transition-Metal Atom Adsorption on an Fs Defect Site of MgO (100) and the Interaction with a Hydrogen Atom. E.Florez, F.Mondragón, T.N.Truong, P.Fuentealba: Physical Review B, 2006, 73[11], 115423 (7pp)