Seminar by Auguste TETENOIRE (Institut des Sciences Chimiques de Rennes)

Toward large computational cell: application of DFTB parametrized method for molecules on metal surfaces

Auguste TETENOIRE

Univ Rennes, CNRS, ISCR (Institut des Sciences Chimiques de Rennes) – UMR 6226, F-35000 Rennes, France

The complexity to interpret experimental results lead to a large development of the theoretical methods to help understanding the underlying mechanisms. Within all the theoretical method, the Density Functional Theory (DFT) is one of the most widely used. However, when one will to model a system containing more than hundreds of atoms, the limits in terms of computational cost of the DFT are reached. Therefore, new methods are developed, more approximate but less expensive. Among the parametrize methods, the Density Functional Tight Binding (DFTB) shows great successes in modeling large system while keeping access to the quantum properties of the systems, e.g. atomic orbitals.

Here we apply this method to characterize the interaction between macrocycle calix[4]arene molecule and gold surfaces. We first investigate the grafting properties of the molecules on the gold (111) facet, being the one with the lowest surface energy. Then we compute Raman spectra and compare with experimental results to clarify the grafting mechanism. The very good agreement between theory and experiment allows to prove the covalent grafting between the organic molecule and the surface, as well as it brings comprehension in the grafting mechanism. Finally, we push the investigation to different gold facets, prior to simulate the full nano-objects.