Berlin 2008 – wissenschaftliches Programm
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SYMP: Symposium Computational Soft matter physics
SYMP 2: Computational soft matter physics
SYMP 2.7: Vortrag
Donnerstag, 28. Februar 2008, 16:45–17:00, H 0105
Reproducibility of single particle-dynamics. The Hori-type generalized Langevin equation — •Jörg R. Silbermann1, Sabine H. L. Klapp1,2, and Martin Schoen1 — 1Stranski-Lab für Physikalische und Theoretische Chemie, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin — 2Institut für Theoretische Physik, Technische Universität Berlin, Strasse des 17. Juni 124, 10623 Berlin
We consider the dynamics of a single tagged particle of mass M in a 2D Lennard-Jones (LJ) system. Employing the Mori-Zwanzig projector operator formalism, one can derive [1] an effective equation of motion of the form of a generalized Langevin equation (GLE). The ”random force” F0r(t) appearing in the GLE is in general unknown. For a harmonic solid, however, one can derive a GLE where F0r(t) coincides with the total force F0*(t) acting on the tagged particle in a ”reference system”, where the mass is changed from M to an arbitrary mass m*. We study to what extent this GLE is still able to capture the dynamics of the tagged particle under conditions where the harmonic approximation is no longer justified. To this end we compute typical time-autocorrelation functions for the tagged particle in molecular dynamics simulations for the full LJ system and compared those with the ones from the GLE. We find excellent agreement at low temperatures and a surprisingly good reproduction of the dynamics even in the high-temperature liquid phase.
[1] K. Wada, J. Hori, Prog. Theor. Phys. 49, 129, (1973).