Translational friction and momentum dissipation of a solute in simple liquid studied by generalized Langevin theory for liquid under external field

The translational friction coefficients on spherical solutes in the Lennard-Jones liquid are calculated as the function of solute size and the strength of the solute-solvent attractive interaction using the generalized Langevin theory for simple liquids under external fields recently proposed by us [T. Yamaguchi, T. Matsuoka, and S. Koda, J. Chem. Phys., 123 (2005) 034504.]. When the solute is as small as the solvent, the friction coefficient is a strong function of the solute-solvent attractive interaction, which means that it is the solute-solvent interaction rather than the solvent viscosity that determines the translational friction on the solute. On the other hand, when the solute is eight times larger than the solvent, the dependence on the solute-solvent attractive interaction becomes weak, indicating the dominant role of the solvent viscosity. The transient momentum transfer from the solute to the solvent is analyzed in connection with the crossover from microscopic to continuum views of the solvent.