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Dresden 2009 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 39: POSTERS Colloids and Liquids

CPP 39.18: Poster

Thursday, March 26, 2009, 17:00–19:30, P3

Modeling effective single–particle dynamics by the harmonic chain method — •Jörg R. Silbermann, Michael Melle, and Martin Schoen — Stranski-Laboratorium für Physikalische und Theoretische Chemie, Technische Universität Berlin, D-10623 Germany

We consider the dynamics of a single tagged particle in a Lennard–Jones (LJ) system. Based on the equivalent harmonic chain method introduced by Adelman [1] a coarse grained description of the full many body system is generated. In this description the influence of the ’bath’ surrounding the tagged particle is captured by means of a N-atom nearest neighbour harmonic chain. This chain is completely defined by a set of Einstein frequencies {ωen2} and coupling constants {ωcn2} that can be determined from the memory function M(t) linked to the velocity autocorrelation function (VACF) of the tagged particle in the LJ system [2]. In our work we assume M(t) to be Gaussian. While this ansatz completely neglects long-time collective effects, M(t) is then completely defined by static properties of the full LJ system that can be easily obtained from short Molecular Dynamics simulation runs. We study the influence of chain-length N on the dynamics of the tagged particle. Moreover, we investigate systematically the impact of the specific thermodynamic conditions (i.e., temperature and density) on the performance of our approach.
[1] S. A. Adelman, J. Chem. Phys. 71, 4471 (1979).
[2] M. Berkowitz, C. L. Brooks III, and S. A. Adelman, J. Chem. Phys. 72, 3889 (1980).

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