Dresden 2003 – wissenschaftliches Programm

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O: Oberflächenphysik

O 24: Postersitzung (Epitaxie und Wachstum, Oxide und Isolatoren, Elektronische Struktur, Oberfl
ächenreaktionen, Adsorption an Oberfl
ächen, Organische Dünnschichten)

O 24.47: Poster

Mittwoch, 26. März 2003, 14:30–17:30, P1

Local reactivity of Pd overlayers and clusters deposited on Au — •Ata Roudgar and Axel Groß — Physik-Department T30, Technische Universität München, 85747 Garching, Germany.

The local reactivity of thin pseudomorphic Pd overlayers and small Pd clusters deposited on Au single crystal surfaces has been studied by density functional theory (DFT) calculations within the generalized gradient approximation. We have determined the adsorption energies of atomic hydrogen and of CO as a microscopic probe of the reactivity. As for the overlayers, we find that both surface strain and substrate interaction effects contribute significantly to the modification of the reactivity of the overlayer system, leading to a maximum in the binding energies on two Pd overlayers on Au.

Furthermore, according to the DFT calculations the supported Pd clusters are much less reactive than the corresponding clusters in the gas-phase. The H and CO adsorption energies on the supported Pd clusters are even smaller than on the pseudomorphic Pd/Au overlayers. The trends in the adsorption energies have been carefully analysed in terms of the underlying electronic structure. It turns out that the contraction of the adsorbed clusters has a decisive influence on their reactivity.