Shear viscosity and dielectric constant in aqueous isopropanol and aqueous acetonitrile

The importance of aqueous mixtures as solvents has motivated the investigation of the usefulness of classical molecular dynamics simulation, using simple effective pair potentials and the Lorentz-Berthelot combining rules, to predict mixture viscosities and dielectric constants. In the acetonitrile-water system, near quantitative agreement with experiment is found; however, the calculated shear viscosity in the 2-propanol-water system is underpredicted by more than a factor of two. Moreover, the results do not appear to be strongly dependent on the mixture combining rules, as a 10% decrease in the unlike OO Lennard-Jones size parameter for this system had no discernable effect on the calculated viscosity. In both systems, the dielectric constant predictions were in qualitative accord with experiment, although systematically underpredicted as in the pure component models.