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).