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O: Fachverband Oberflächenphysik

O 14: Organic/bio Molecules on Metal Surfaces II

O 14.7: Vortrag

Montag, 31. März 2014, 17:30–17:45, TRE Phy

Charged adsorbates among each other: Simulating intermolecular interactions of free-base porphine on coinage metal surfaces — •Moritz Müller, Reinhard J. Maurer, Katharina Diller, and Karsten Reuter — Technische Universität München

Designed through the process of evolution, porphine naturally serves as a basic unit in hemeproteins and chlorophyll. Functionality and robustness of these compounds suggest potential applications tackling photovoltaics, nano-catalysis, data storage, and drug design. Many technical realizations require controllable surface engineered coating of ordered molecular films on two-dimensional boundaries. Adsorbed to coinage metal surfaces, porphine overlayers exhibit a variety of different superstructures [1], depending on the coverage. We report modeling of free-base porphine on clean Ag(111) and Cu(111) surfaces in the framework of dispersion-corrected semi-local Density Functional Theory. The lateral interactions determining the overlayer structure can be expressed as two competing forces: attractive van-der-Waals interactions and repulsive electrostatic interactions between the charge-transfer-induced adsorbate dipoles. Our investigations of the adsorption geometries and the electronic structure display, in agreement with experiment, a substantial amount of charge-transfer to the molecule upon adsorption. Based on our ab-initio calculations a simple interaction model is introduced and corresponding conclusions are drawn towards the coverage-dependent supermolecular arrangement and the effects of adsorbate functionalization.

[1] F. Bischoff et al., ACS Nano, 7, 3139 (2013)