Simulation of a Single Polymer Chain in Solution by Combining Lattice Boltzmann and Molecular Dynamics

TL;DR

This paper introduces a novel simulation method combining lattice Boltzmann and molecular dynamics to efficiently model a polymer chain in solution, validated against analytical theory and existing MD simulations, enabling larger time steps.

Contribution

A new coupled lattice Boltzmann and molecular dynamics method for simulating polymer-solvent systems with validated accuracy and improved efficiency over traditional MD.

Findings

The method accurately reproduces static and dynamic properties of a single polymer chain.

Finite size effects on decay rates follow an L^{-3} scaling, different from other properties.

The new approach allows for larger simulation time steps compared to standard MD.

Abstract

In this paper we establish a new efficient method for simulating polymer-solvent systems which combines a lattice Boltzmann approach for the fluid with a continuum molecular dynamics (MD) model for the polymer chain. The two parts are coupled by a simple dissipative force while the system is driven by stochastic forces added to both the fluid and the polymer. Extensive tests of the new method for the case of a single polymer chain in a solvent are performed. The dynamic and static scaling properties predicted by analytical theory are validated. In this context, the influence of the finite size of the simulation box is discussed. While usually the finite size corrections scale as L^{-1} (L denoting the linear dimension of the box), the decay rate of the Rouse modes is only subject to an L^{-3} finite size effect. Furthermore, the mapping to an existing MD simulation of the same system is done so that all physical input values for the new method can be derived from pure MD simulation. Both methods can thus be compared quantitatively, showing that the new method allows for much larger time steps. Comparison of the results for both methods indicates systematic deviations due to non-perfect match of the static chain conformations.