Simulations of solvation dynamics in simple polar solvents

This paper describes the results of computer simulations of charge solvation dynamics in a Stockmayer solvent (Lennard-Jones spheres with point dipoles at their centers). The solvent molecules are characterized by mass and moment of inertia which can be varied independently, thus providing the possibility to study the separate effects of the rotational and translational solvent motions on the solvation process. We focus on the role played by these degrees of freedom, and on the contributions of different solvation shells around the solute to the solvation process in order to check the validity of recently proposed theories of solvation dynamics. We find that even in this structureless solvent, as in the more structured solvents studied earlier, inertial effects dominate the solvation process, and dielectric solvation theories which do not take into account these effects cannot describe the observed dynamics. The dynamic mean spherical approximation and generalized diffusion theories cannot account for the observed dynamics even when solvent translations are frozen.