Hannover 2016 – scientific programme

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MO: Fachverband Molekülphysik

MO 18: The Modelling of Molecular Dynamics

MO 18.1: Talk

Thursday, March 3, 2016, 14:30–14:45, f142

Caldeira-Leggett Model Description of Condensed Phase Vibrational Spectroscopy — •Fabian Gottwald, Sergei D. Ivanov, and Oliver Kühn — Institut für Physik, Universität Rostock, Rostock

Formulating a rigorous system-bath partitioning approach remains an open issue. In this context the popular Caldeira-Leggett (CL) model enables simple modeling of system-bath interactions via spectral density functions. For parametrizing spectral densities we propose a Fourier-based method that outperforms existing time-domain methods [1]. Moreover, the widely used rigid bond method turns out to be inappropriate and leads to a systematic overestimation of relaxation times, unless the system under study is indeed of CL form. The validity of the CL model for describing anharmonic dynamics of real systems is often taken for granted. It is shown that such a use does not pass the self-consistency check for a broad class of solute-solvent systems, unless the system part of the potential is effectively harmonic [2]. The check is performed by comparing the spectra resulting from the corresponding generalized Langevin dynamics with their counterparts from explicit classical molecular dynamics. Although there exist systems that can be mapped onto the CL model, no a priori criteria are found and the ultimate verdict is provided by the self-consistency check only.
[1] F. Gottwald, S. Karsten, S. D. Ivanov, O. Kühn. J. Chem. Phys. 142, 244110 (2015).
F. Gottwald, S. D. Ivanov, O. Kühn. J. Phys. Chem. Lett. 6, 2722 (2015).