Regensburg 2004 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

O: Oberflächenphysik

O 14: Postersitzung (Adsorption an Oberflächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Phasenübergänge, Rastersondentechniken, Struktur und Dynamik reiner Oberflächen)

O 14.5: Poster

Montag, 8. März 2004, 18:00–21:00, Bereich C

Adsorption energies on bimetallic overlayer systems at the solid-vacuum and solid-liquid interface — •Ataollah Roudgar and Axel Groß — Physik-Department T30g, Technische Universität München, James-Franck-Strasse 1, 85747 Garching, Germany

We have determined the adsorption energies of atomic hydrogen and of CO on bimetallic surfaces as a microscopic probe of the reactivity. The calculations have been performed using density functional theory (DFT) calculations within the generalized gradient approximation. For PdCu bimetallic surfaces, we find a rather strong interaction between the Pd and Cu atoms. Consequently, both Pd/Cu and Cu/Pd overlayer systems exhibit an intermediate behavior between pure Cu and pure Pd. This is in contrast to the sustem Pd/Au where both the expansion of the pseudomorphic Pd overlayers and the relatively weak interaction between Pd and Au lead to hydrogen and CO adsorption energies that are even larger than on clean Pd surfaces.

Furthermore, we have studied the local reactivity of one layer pseudomorphic Pd overlayers on Au(111) surface in the presence of a water layer. We find a two-dimensional ice-like hexagonal structure of water on the metal surface to be energetically most favorable. We also find that the water-metal interaction is rather weak. The hydrogen and CO adsorption energies are changed by less than 5% and 10%, respectively, by the presence of water. This indicates that theoretical adsorption studies at the solid-vacuum interface might also be relevant for the solid-liquid interface.