Regensburg 2010 – wissenschaftliches Programm

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DS: Fachverband Dünne Schichten

DS 31: Molecular Spintronics - Current Status and Challenges I (Focused Session)

DS 31.6: Topical Talk

Donnerstag, 25. März 2010, 12:15–12:45, H2

Role of the van der Waals interaction on the adsorption of organic molecules on surfaces — •Nicolae Atodiresei — Institut für Festkörperforschung, Forschungszentrum Jülich

The design of nanoscale molecular elements in multifunctional devices relies on a clear understanding of the physics at electrode-molecule interfaces with a particular emphasis on the functionality of specific molecules in a given organic-inorganic surface environment. Using ab initio simulations and appropriate methods to account for the long-range dispersion effects we have performed studies on several organic molecules adsorbed on non-magnetic and ferromagnetic surfaces. Our results show that the alignment of the molecular orbitals at adsorbate-substrate interface depends on the number of heteroatoms present in an aromatic ring and, as a direct consequence, for a flat adsorption geometry, the molecule-surface van der Waals interaction involves not only the π-like orbitals which are perpendicular to the molecular plane but also σ-like orbitals delocalized in the molecular plane. In the case of perpendicular adsorption geometries we demonstrate that the position of the heteroatoms in the aromatic rings can be used to precisely tune the HOMO-LUMO gap making possible a chemical identification of the specific molecular species embedded into a molecular layer. Furthermore, our calculations demonstrate that, for specific types of organic molecules, taking into account the non-local correlation effects responsible for the long range van der Waals interaction is essential to correctly describe the charge transfer at the interface which yields the formation of molecule-surface hybrid states.