Excitation and reaction at metal and oxide surfaces: cluster models help to interpret experiments

Klaus Hermann 

Max-Planck-Gesellschaft, Fritz-Haber-Institut, Faradayweg 4-6, Berlin D-14195, Germany

Abstract

This talk reviews recent theoretical work on electronic and structural properties of metal and oxide surfaces including adsorption and reaction of small molecules where density functional theory (DFT) and embedded surface cluster models have been used. Differently coordinated surface oxygen in vanadium oxides exhibits pronounced differences in its charging and binding, which influences the surface geometry and indicates different chemical behavior as identified by surface sensitive spectroscopies. Results from recent theoretical spectroscopy studies on vanadium pentoxide, V2O5, will be discussed in detail and compared with experimental data.

Surface oxygen binds very strongly to the substrate as determined by corresponding vacancy energies for the V2O5 surface. Further, surface vacancies are found to serve as chemically active centers inducing chemical reduction of nearby metal sites. This is obvious from atom projected densities of states and has been confirmed by experiment.

Extended cluster studies on different phenylpropene adsorbates on Cu(111) substrate yield equilibrium geometries which are consistent with experimental findings based on angle-resolved NEXAFS measurements. In particular, the theoretical angle-resolved spectra evaluated in the cluster approach are in excellent agreement with all details of the experimental NEXAFS data. The comparison between theory and experiment can explain the different epoxidation rates of the adsorbates by simple geometric effects.

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Presentation: Keynote lecture at E-MRS Fall Meeting 2006, Symposium B, by Klaus Hermann
See On-line Journal of E-MRS Fall Meeting 2006

Submitted: 2006-05-04 10:14
Revised:   2009-06-07 00:44
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