Solute molecular dynamics in a mesoscale solvent

A hybrid molecular dynamics (MD) algorithm which combines a full MD description of solute-solute and solute-solvent interactions with a mesoscale treatment of solvent-solvent interactions is developed. The solvent dynamics is modeled on a mesoscale level by coarse graining the system into cells and updating the velocities of the solvent molecules by multiparticle collisions within each cell. The solvent dynamics is such that the correct hydrodynamic equations are obtained in the macroscopic limit and a Boltzmann distribution of velocities is established in equilibrium. Discrete-time versions of the hydrodynamic equations and Green-Kubo autocorrelation functions are derived. Between the discrete-time solvent-solvent collisions the system evolves by the classical equations of motion. The hybrid MD scheme is illustrated by an application to the Brownian motion of a nanocolloidal particle in the mesoscale solvent and concentrated nanocolloidal suspensions. (C) 2000 American Institute of Physics. [S0021-9606(00)50816-2].