Theory

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In close collaboration with the other funCOS projects, funCOS 6 focuses on a comprehensive theoretical atomic-scale understanding of the adsorbate-substrate and adsorbate-adsorbate interactions of functionalized organic molecules on structured metal-oxide surfaces, with the aim to eventually enable a controlled formation of organic films with specific structural, electronic and optical properties. Means to alter the adsorbate-substrate interaction are the substitution of organic molecules with specific linker groups or the modification of the substrate, for instance via a surface hydroxylation. In this way, adsorption sites and geometries on pristine surfaces or at low-coordinated sites at nano-structured metal-oxide substrates may be influenced. The adsorbate-substrate interaction includes chemical reactions like the self-metallization of porphyrins. The adsorbate-adsorbate interaction, which hinges on the adsorbate-substrate interaction via the distance between adjacent adsorption sites, can be tuned via functional groups. The funCOS theory area pursues theoretical modeling of these topics based on density- functional theory supplemented by Van-der-Waals corrections and Hubbard-U approaches, ab initio molecular dynamic simulations, and additional high-level electronic structure methods, i.e. time-dependent density functional theory, many-body perturbation theory (GW/BSE), and wave- function-based methods. Investigations will take up the knowledge gained in the first funding period of funCOS on linker molecules, networks of smaller organic molecules, and metalation reactions of functionalized porphyrins. Metal adatoms in combination with functionalized organic molecules may open new opportunities to create 2D metal-organic networks. Modeling will predict which combinations of adatoms and linker groups are promising for the self-assembly of such networks. The metal-oxide substrate is a key element of structure formation and thus a topic of investigations regarding its electronic properties and low-coordinated sites such as surface defects, metal adatoms or hydroxyl groups. The surfaces of MgO, TiO2, and different cobalt oxides and corresponding thin oxide films on metals, specifically MgO/Ag(100), CoO(100)/Ir(100), and Co3O4(111)/Ir(100) will be investigated. In this respect, novel nanoparticle systems, like Mg(1-x)Co(x)O nanocrystals and MgO nanocube stacks, are of particular interest as they feature Co atoms at the surface, surfaces of different orientation and connecting elements as adsorption sites for functional molecules. Deposition of large organic molecules from solution is a very appealing, experimentally easy to handle alternative to the gas phase preparation. To take ab initio modeling beyond the surface science approach to the metal oxide/liquid interface is a huge step. The funCOS theory area will investigate interactions of liquids with metal oxides and chemical reactions at the liquid/oxide interface.