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O: Oberflächenphysik
O 46: Adsorption an Oberfl
ächen V
O 46.2: Talk
Tuesday, March 8, 2005, 16:00–16:15, TU EB420
Partial Dissociation of Water on the ZnO(1010) Surface — •B. Meyer1, D. Marx1, O. Dulub2, U. Diebold2, M. Kunat3, D. Langenberg3, and Ch. Wöll3 — 1LS für Theoretische Chemie, Ruhr-Universität Bochum — 2Dept. of Physics, Tulane University, New Orleans, USA — 3LS für Physikalische Chemie I, Ruhr-Universität Bochum
The delicate interplay between chemical bonding, van der Waals forces, and hydrogen bonding gives rise to complex phenomena such as complete dissociation, partial dissociation at defects, molecular adsorption, and multilayer formation when H2O interacts with solid surfaces. Recently, an intriguing, yet controversial, intermediate scenario was advanced, where the interaction between water molecules results in a partial dissociation of H2O on perfect surfaces, leading to superlattices with long-range order. In a combined theoretical and experimental study, applying DFT calculations, Car-Parrinello molecular dynamics simulations, and STM computations, together with diffraction (He-atom scattering, LEED), STM, and thermodynamic measurements we give conclusive evidence that such a phenomenon is encountered for H2O on the perfect ZnO(1010) surface. At monolayer coverage, every second water molecule is found to auto-dissociate, subject to a low activation barrier, upon a favorable hydrogen-bonding interaction with a neighboring water molecule, i.e. without the need to invoke defects or impurities. This process leads to a (2×1) superlattice with long-range order which is stable from below 200 K up to temperatures close to the boiling point of liquid water. [1] B. Meyer, D. Marx, O. Dulub, U. Diebold, M. Kunat, D. Langenberg, Ch. Wöll, Angew. Chem., in print.