Dresden 2011 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 49: Metal substrates: Adsorption of organic / bio molecules VI
O 49.4: Vortrag
Mittwoch, 16. März 2011, 15:45–16:00, PHY C213
Conformations of tetra(phenyl)porphyrine on Au(111): identification by experiment and theory — •Felix Hanke1, Johannes Mielke2, Leonhard Grill2, and Mats Persson1 — 1University of Liverpool, Liverpool, UK — 2Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin
The on-surface synthesis of covalently coupled networks of tetra (phenyl)-porphyrines (TPP) on Au(111) [1] is a significant step toward custom-designed molecular structures. This is particularly useful as single TPP molecules adsorbed on Au(111) and imaged with a scanning tunneling microscope show several distinct configurations, which could be used for information storage. Here we present a combined density functional (DFT) and scanning tunneling microscopy study to elucidate the nature of the observed conformers. They differ in the internal structure of the porphyrin core which can be either flat or buckled. We further assess the importance of accounting for dispersion interactions in the adsorbate-surface coupling by comparing DFT results using the van der Waals density functional (vdw-DF) [2] and the PW91 functional. While the vdw-DF is found to significantly alter both adsorption height and binding energy of TPP, it hardly affects either its internal geometry or the electronic structure, suggesting that TPP is largely decoupled from the substrate.
[1] L. Grill et al., Nature Nanotech., 2 687 (2007). [2] J. Klimeš is acknowledged for his implementation of the vdw-DF density functional.