Charge separation and covalent bonding in metal oxide surfaces: A local density functional study on the MgO(001) surface
- Lehrstuhl fuer Theoretische Chemie, Technische Universitaet Muenchen, 85747 Garching (Germany)
- Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545 (United States)
A first principles local density functional investigation on extended, two-dimensional periodic slab models of the MgO(001) surface is performed, using the linear combination of Gaussian-type orbitals (LCGTO) technique as implemented in the FILMS program package. Stimulated by recent theoretical evidence for a reduced charge separation in MgO(001), a detailed analysis of the charge distribution and its influence on the electrical field above the surface is carried out. Two different methods to quantify the charge separation in the ionic substrate are employed, a local one based on the topological atom approach and a global one derived from the Madelung field of the surface near potential adsorbates. Both procedures lead to a charge separation significantly (10%--20%) below the nominal ionic value of [plus minus]2 a.u. A variational atomic orbital analysis is utilized to discuss the origin of the Mg 3[ital s] and 3[ital p] structures discernible in the crystal orbitals of the MgO slab systems. They are identified as covalent magnesium valence orbital admixtures to the oxygen dominated valence bands in consistence with the reduced charge separation. Their influence on the cohesive energy of crystalline MgO, however, is found to be only 5% ([similar to]0.5 eV).
- OSTI ID:
- 5117390
- Journal Information:
- Journal of Chemical Physics; (United States), Vol. 100:9; ISSN 0021-9606
- Country of Publication:
- United States
- Language:
- English
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