Dresden 2009 – wissenschaftliches Programm
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DF: Fachverband Dielektrische Festkörper
DF 3: Focus Session: Interactions of Molecules with Dielectric Surfaces
DF 3.7: Topical Talk
Montag, 23. März 2009, 17:00–17:20, WIL A317
Adsorption of Organic Molecules on Moderately Reactive Substrates — •Michael Rohlfing1, Andreas Greuling1, and Thomas Bredow2 — 1Fachbereich Physik, Universität Osnabrück, Germany — 2Institute for Physical and Theoretical Chemistry, Universität Bonn, Germany
We discuss the adsorption of organic molecules on crystal surfaces within density-functional theory (DFT), focusing on three examples of moderate molecule-substrate interaction. PTCDI, which is a flat elongated molecule, binds to rutile TiO2(110) in a flat-lying configuration with orientation along the rows, showing high mobility along the rows. TMA, on the other hand, interacts with rutile TiO2(110) via COOH groups at preferred sites, resulting in specific, flat-lying configurations. Thirdly, PTCDA adsorbs on Ag(111) by delocalized interaction of its perylene core plus local binding via its oxygen corner groups. All results are discussed in context with available experimental data.
Our studies demonstrate very different relaxation time scales of intramolecular and molecule-substrate coordinates, driven by the much different respective energies. This requires particular care in all optimization procedures. Furthermore, we discuss the validity of various exchange-correlation functionals, in comparison with more advanced adsorption energies from an exact-exchange-and-correlation (EXX+RPA) formalism. Our EXX+RPA and DFT results for PTCDA/Ag(111) demonstrate that the most reliable DFT data are obtained from the local-density approximation (LDA), which we use throughout our DFT studies, therefore.