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O: Oberflächenphysik

O 41: Electronic structure III

O 41.2: Vortrag

Donnerstag, 30. März 2006, 15:15–15:30, WIL B321

Electronic structure of molybdenum dioxide. Periodic and cluster DFT quantum chemical studies. — •Renata Tokarz-Sobieraj, Malgorzata Witko, and Robert Grybos — Institute of Catalysis and Surface Chemistry, PAS, Cracow, Poland

DFT method is used to describe the electronic structure of bulk and catalytically interesting (011) surface of molybdenum dioxide. MoO2 exists in literature mainly as a product of MoO3 reduction; however, the problem of its role in catalytic processes is still unsolved. The electronic structure of bulk system is calculated using periodic approach (VASP code), whereas the information of monoclinic (011) surface is obtained from the cluster method (StoBe code). In both calculations the gradient corrected functionals are used. Detailed analyses of total and atom projected density of states (DOS, PDOS) yield metallic behavior for MoO2 bulk material. The band around the Fermi level is mainly of Mo 4d character, whereas directly below - there are the O 2p bands (up to -3eV). Further, below EF there is a band (from -3 to -8 eV) identified as Mo-O bonding molecular orbitals. Local properties of different surface sites that are exposed at (011) surface, namely five- and six- fold coordinated Mo atoms, and nucleophillic O sites with different coordination numbers are discussed using charge densities, bond orders indices and molecular orbital diagrams. The discussed surface is characterized by DOS spectra similar to the bulk. Pairs of metallic sites and isolated oxygen centers are identified.