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O: Fachverband Oberflächenphysik

O 59: Poster Session II (Nanostructures at surfaces: Dots, particles, clusters; Nanostructures at surfaces: arrays; Nanostructures at surfaces: Wires, tubes; Nanostructures at surfaces: Other; Plasmonics and nanooptics; Metal substrates: Epitaxy and growth; Metal substrates: Solid-liquid interfaces; Metal substrates: Adsoprtion of organic / bio molecules; Metal substrates: Adsoprtion of inorganic molecules; Metal substrates: Adsoprtion of O and/or H; Metal substrates: Clean surfaces; Density functional theory and beyond for real materials)

O 59.89: Poster

Mittwoch, 24. März 2010, 17:45–20:30, Poster B1

Diffusion of 1,4-butanedithiol radicals on Au(111) and Au(100): A DFT-based comparison — Andreas Franke and •Eckhard Pehlke — Institut für Theoretische Physik und Astrophysik, Universität Kiel, 24098 Kiel, Germany

Organic molecules chemisorbed on surfaces hold the perspective of surface functionalization. The 1,4-butanedithiol radical chemisorbed at the Au(111) or Au(100) surface serves as a model system for the S-Au molecule-substrate bond. Density functional total-energy calculations have been carried out for the chemisorption of the radical on the unreconstructed Au surfaces, which are both known to be stabilized under electrochemical conditions [1]. Local minima with close-by energies indicate multi-valley potential-energy surfaces, which originate from the interplay between the two S-Au adsorbate-substrate bonds and the internal degrees of freedom of the butanedithiol radical. Diffusion paths of the radical on both Au surfaces have been calculated within DFT using VASP [2]. The diffusion barriers for translation and rotation of the radical differ. They can be fine-tuned by varying the applied potential in the electrochemical cell. This is considered theoretically by inspecting the variation of the dipole moment along the reaction paths. Consequences for the dynamics of succeeding diffusion hops are discussed.

[1] M. Schneeweiss et al., Appl. Phys. A 69, 537 (1999). H. Striegler et al., J. Electroanal. Chem. 471, 9 (1999).

[2] http://cms.mpi.univie.ac.at/vasp