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MM: Fachverband Metall- und Materialphysik

MM 10: Methods in Computational Materials Modelling (methodological aspects, numerics)

MM 10.3: Vortrag

Montag, 1. April 2019, 16:15–16:30, H45

Parametrization of classical force fields for single molecule junctions — •Narendra P. Arasu and Hector Vazquez — Institute of Physics of the Czech Academy of Sciences, Cukrovarnicka 10, Prague, Czech Republic

In molecular junctions, where single molecule bridges the gap between metal electrodes, interface geometry under the influence of thermal fluctuations can be explored from Molecular Dynamics (MD) simulations. Ab-initio methods are accurate but their computational cost restricts the time scale that can be probed in the simulations. Thus, simulations based on Density Functional Theory (DFT) can be limited to rather restricted phase-space. On the other hand, Molecular Mechanics (MM) simulations are computationally faster than DFT. However, careful parametrization of the MM energy functions is required for realistic representation of an MD ensemble. In this work, we propose a method to parametrize Optimized Potentials for Liquid Simulations (OPLS-AA) forcefield to run a long time scale (~ nanoseconds) MD simulations. The parameters are obtained by fitting the model energy functions of short-range interactions to the energies from DFT calculations. As a prototypical molecular junction, we consider a biphenyl molecule with three different linker groups having different chemical binding: Au-C, Au-NH2, and Au-SCH3 to test our parametrization technique. We compare the statistics of changes in bond lengths, angles and dihedrals obtained from classical MD trajectories to that of the ab-initio MD simulations. The results show that the parameters obtained using our method describe well DFT MD simulations.