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O: Fachverband Oberflächenphysik
O 12: Oxides and insulators: Adsorption
O 12.4: Vortrag
Montag, 22. März 2010, 15:45–16:00, H33
Anomalous molecular orbital variation upon adsorption on wide band gap insulator: Gluconic acid on MgSO4·H2O(001) — •Wei Chen1, Christoph Tegenkamp1, Herbert Pfnür1, and Thomas Bredow2 — 1Institut für Festkörperphysik, Leibniz Universität Hannover, Hannover, Germany — 2Institut für Physikalische und Theoretische Chemie, Universität Bonn, Bonn, Germany
The understanding of the interaction between organic molecule and wide band gap insulator is of great importance provided with their elementary roles in organic electronics and optoelectronic devices. It is commonly believed that organic molecules are physisorbed on the ideal non-polar surface of wide band gap insulator with limited variation on the electronic properties of the adsorbate molecule. However, on the basis of first principles calculation on the gluconic acid adsorbed on the (001) surface of a ternary compound MgSO4·H2O, we show that the orbitals of the acid molecule could undergo significant changes upon adsorption. The gluconic acid binds strongly to the MgSO4·H2O(001) via multiple electrostatic interactions from Mg-O, which is further stabilized by the long range dispersion force. The electrostatic interactions result in a pronounced intra-molecular distortion of the adsorbate, yielding a much smaller HOMO-LUMO gap of the acid due to the geometrical change alone. Furthermore, as manifested by the prominent hybridization between the molecule and the surface, the characteristics of the frontier orbital are modified significantly upon adsorption with respect to the isolated molecule.