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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 59.57: Poster
Mittwoch, 24. März 2010, 17:45–20:30, Poster B1
Adatoms with character: Co and Pt atoms on Pt (111) — •Andreas Garhofer1,2, Zuzana Bortlova1, Michael Schmid1, Peter Varga1, and Josef Redinger1,2 — 1Institut f. Angewandte Physik, TU Wien — 2Center for Computational Materials Science, TU Wien
Surface diffusion of Co adatoms on Pt(111) has been studied by first principles DFT methods, implemented in the program package VASP and STM. A diffusing Co adatom jumps over bridge sites between two surface Pt atoms from stable fcc to hcp sites and vice versa. The calculated barrier of 0.194 eV is in good agreement with recent experiments (0.200 eV) [1]. Adding a second Co adatom at the largest separation possible on a (5x5) surface unit cell reveals a repulsive interaction between the Co adatoms, presumably due to unfavorable relaxations imposed on the Pt substrate, while magnetic interactions could be ruled out. Only if the two Co atoms come close together a stable dimer is formed. Both theoretical findings agree well with our STM observations. Mimicking the onset of growth of Co layers, calculations for three Co adatoms confirm our STM experiments by predicting a triangular Co adatom configuration to be most stable. Surprisingly, the results for three (four) Pt adatoms on Pt(111) are different. In contrast to Co, Pt adatoms behave "strange" and prefer linear configurations instead of maximizing the number of nearest neighbor bonds.
[1] P. Buluschek, thesis No. 3944, Ecole Polytechnique federale de Lausanne (2007)