Simulation of a single polymer chain in solution by combining lattice Boltzmann and molecular dynamics

In this paper we establish a new efficient method for simulating polymer-so lvent systems which combines a lattice Boltzmann approach for the fluid wit h 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 tes ts of the new method for the case of a single polymer chain in a solvent ar e performed. The dynamic and static scaling properties predicted by analyti cal theory are validated. In this context, the influence of the finite size of the simulation box is discussed. While usually the finite size correcti ons scale as L-1 (L denoting the linear dimension of the box), the decay ra te of the Rouse modes is only subject to an L-3 finite size effect. Further more, the mapping to an existing MD simulation of the same system is done s o that all physical input values for the new method can be derived from pur e MD simulation. Both methods can thus be compared quantitatively, showing that the new method allows for much larger time steps. Comparison of the re sults for both methods indicates systematic deviations due to nonperfect ma tch of the static chain conformations. (C) 1999 American Institute of Physi cs. [S0021-9606(99)50840-4].