Combining molecular dynamics with Lattice Boltzmann: A hybrid method for the simulation of (charged) colloidal systems

Abstract

We present a hybrid method for the simulation of colloidal systems that combines molecular dynamics (MD) with the Lattice Boltzmann (LB) scheme. The LB method is used as a model for the solvent in order to take into account the hydrodynamic mass and momentum transport through the solvent. The colloidal particles are propagated via MD and they are coupled to the LB fluid by viscous forces. With respect to the LB fluid, the colloids are represented by uniformly distributed points on a sphere. Each such point [with a velocity V(r) at any off-lattice position r] is interacting with the neighboring eight LB nodes by a frictional force F = xi0(V(r)-u(r)), with xi0 being a friction coefficient and u(r) being the velocity of the fluid at the position r. Thermal fluctuations are introduced in the framework of fluctuating hydrodynamics. This coupling scheme has been proposed recently for polymer systems by Ahlrichs and Dunweg [J. Chem. Phys. 111, 8225 (1999)]. We investigate several properties of a single colloidal particle in a LB fluid, namely, the effective Stokes friction and long-time tails in the autocorrelation functions for the translational and rotational velocity. Moreover, a charged colloidal system is considered consisting of a macroion, counterions, and coions that are coupled to a LB fluid. We study the behavior of the ions in a constant electric field. In particular, an estimate of the effective charge of the macroion is yielded from the number of counterions that move with the macroion in the direction of the electric field.

Lattice Boltzmann Simulations of Soft Matter Systems

“…This method has the advantage of greatly reducing the number of LB grid points in the simulation, at the cost of a representation that is only correct in the far field. The method has been applied to polymers [43,122,123] and to suspended solid particles [124][125][126][127][128]. In the latter case the surface is described by a number of sources distributed over the surface of the particle.…”

“…However, the coupling in this case is implicit, solving for the velocity of the interface through a force balance, which corresponds to the high friction limit of Refs. [124][125][126][127][128]. Here, we will only consider inertial coupling, since the theory for thermal fluctuations has not been worked out for the implicit schemes.…”

Simulation of DNA electrophoresis in systems of large number of solvent particles by coarse‐grained hybrid molecular dynamics approach

“…One combines MD with BD for simulating the particle Brownian motion. 25 The second combines MD with lattice Boltzmann for studying electrophoretic properties of highly charged colloids, [26][27][28] and the third combines MD with mesoscale treatment of solvent-solvent interactions for studying solvent effect on polymer dynamics. 20,[29][30][31] By combining the advantages of the coarsegained treatment in CG-MD 17,18 and DPD 22 with the efficient modeling of solvent-solvent interactions of the hybrid MD approach, 23,24,[26][27][28] we introduced and tested a new coarsegrained hybrid MD (CGH-MD) approach as a potentially useful method for complementing the more rigorous methods to simulate systems of larger number of solvent particles without substantially losing simulation accuracy.…”

Lattice-Boltzmann simulation of the sedimentation of charged disks

“…Different implementations of electrokinetic phenomena have been proposed within a lattice-Boltzmann ͑LB͒ scheme [7][8][9][10] and finite-difference methods. 11 We use a LB method introduced previously 12 and which has been shown to perform well when coupling charged solid particles to solvent flows.…”