Dresden 2003 – scientific programme

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SYSE: Simulation and experiment

SYSE 2: Poster (gemeinsam mit SYCN und CPP)

SYSE 2.14: Poster

Tuesday, March 25, 2003, 19:00–21:00, ZEU/250

Effects of the bead–solvent potential on the dynamics of macromolecules — •Alexander Uvarov and Stephan Fritzsche — Universität Kassel, D–34132 Kassel, Germany

The dynamics of a macromolecule, which is immersed in a solvent, is affected not only by interactions among the individual beads of the macromolecule but also by the surrounding solvent particles. In the past, the influence of the solvent has often been taken into account by means of stochastic forces. While, however, this assumption is appropriate for studing the dynamics of macromolecules for long times, recent computer molecular dynamic simulation (MDS) revealed that short–time deviations from a Brownian–type behavior may arise, induced by the discrete (atomistic) structure of the solvent.

In this contribution, we present a Fokker-Planck equation (FPE) which describes the time evolution of the phase–space distribution function of the macromolecule. This FPE includes an explicit expression for the friction tensor which, of course, depends on the bead–solvent potential. In order to explore the effects of different solvent potentials on the molecular dynamics, computation have been carried out for the three cases of a (i) Yakawa, (ii) Born–Mayer, and (iii) Lennard–Jones bead–solvent potential. From the general expression of the center–of–mass friction coefficient of the (N–bead) macromolecule, and by using the Einstein relation, we are able to calculate and compare our results for the center–of–mass diffusion coefficient with MDS [1, 2].

[1] B. Dunweg and K. Kremer, J. Chem. Phys. 99, 6983 (1993);

[2] P. Ahlrichs and B. Dunweg, J. Chem. Phys. 111, 8225 (1999)