Solid State and Optics Seminar
Wednesday, April 19, 2006
1:00 p.m.
107 Mason Lab
"Excitations and Reaction at Metal and Oxide Surfaces:
cluster models can help to interpret experimental data"
Prof. Dr. K. Hermann
Theory Department, Fritz-Haber-Institut der MPG, Berlin (Germany)
and
Sonderforschungsbereich 546 "Transition Metal Oxide Aggregates," Berlin
(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, PES, EELS, NEXAFS, and ELNES. Local binding
becomes also evident from vibrational analyses performed for the surface clusters
where frequencies and intensities can be used to interpret IR, Raman, and EELS
spectroscopy data. Results from recent theoretical spectroscopy studies on vanadium
sesquioxide, V2O3, and vanadium pentoxide, V2O5, will be discussed in detail
and compared with experimental data [1].
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 [2].
[1] C. Kolczewski and K. Hermann, J. Chem. Phys. 118, 7599 (2003).
[2] F. J. Williams, R. L. Cropley, O. P. H. Vaughan, A. J. Urquhart, M. S. Tikhov,
C. Kolczewski, K. Hermann, and R. M. Lambert, J. Am. Chem. Soc., 127, 17007
(2005).
Host: Vic Henrich