Dresden 2006 – scientific programme
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O: Oberflächenphysik
O 32: Adsorption IV
O 32.1: Talk
Thursday, March 30, 2006, 11:15–11:30, TRE Phys
Organic molecules on surfaces: Structural and dynamical properties — •Martin Preuss1, Kaori Seino1, Wolf Gero Schmidt2, and Friedhelm Bechstedt1 — 1Institut für Festkörpertheorie und -optik, Friedrich-Schiller-Universität Jena, Germany — 2Fakultät für Naturwissenschaften, Department Physik, Universität Paderborn, Germany
For the microscopic control of organically functionalized surfaces an understanding on the atomic scale can only be achieved by combined experimental and theoretical studies. For the elucidation of interface structures infrared (IR) and high-resolution electron energy loss spectroscopy (HREELS) are among the most prominent methods due to the sensitivity towards subtle changes in geometry and, hence, vibrational properties. The determination of normal-mode and phonon frequencies belongs to the standard repertoire of density-functional theory (DFT) calculations whereas the corresponding intensities are seldomly reported. We have recently implemented a simple but accurate method into an existing plane-wave DFT code that allows for the calculation of the dynamical dipoles, and thus of IR intensities, for extended systems. For test purposes, the procedure is applied to small isolated molecules (NH3, AlH3, H2O) and to benzene (C6H6) adsorbed on the Si(001) surface. For the system of perylene (C20H12) on Si(001) studied lately we scrutinize a number of possible adsorption configurations and single out the most probable one by comparison of the calculated and the measured vibrational spectrum.