Dresden 2017 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 45: Organic-Inorganic Hybrid Systems and Organic Films

O 45.9: Poster

Dienstag, 21. März 2017, 18:30–20:30, P1A

Computational Phase Diagram Prediction for Organic Monolayers on Metal Substrates — •Lukas Hörmann, Michael Scherbela, Veronika Obersteiner, and Oliver T. Hofmann — Institute of Solid State Physics, NAWI Graz, Graz University of Technology, Austria

Monolayers of organic molecules on inorganic substrates often show rich polymorphism with diverse structures in differently shaped unit cells. Determining the different commensurate structures and their epitaxy matrices from first principles is far from trivial due to the large number of possible polymorphs.

We pursue a novel approach based on coarse-graining the potential energy surface and applying machine learning to efficiently determine the energetically most stable structures. First the adsorption geometries of isolated molecules as well as all possible unique super cells of the substrate are determined. Then all configurations are generated by combining each adsorption geometry with every super cell. For a subset of configurations adsorption energies are determined using dispersion-corrected DFT. This subset serves as training data for a machine learning algorithm, that allows us to predict the adsorption energies for all configurations. Configurations with an adsorption energy below a predefined energy threshold are then probed using DFT.

We demonstrate the capability of our approach for TCNE (tetracyanoethene) on Cu(100) and Naphtalene on Cu(111). We determine the adsorption energies for a large number of polymorphs and compare the results to the experimentally obtained phase diagram.