Dense liquids. II. The effect of density and temperature on viscosity of tetramethylsilane and benzene

Abstract

The effect of temperature and pressure on the shear viscosities of liquid tetramethylsilane and benzene are reported in the dense liquid region. In agreement with molecular dynamics results, the Stokes–Einstein relation is found to be valid at the molecular level for the liquids studied. As expected on the basis of self-diffusion data, the shear viscosities can be explained by using the rough hard sphere model based on the modified Enskog theory of liquids by assuming a temperature dependence of the effective hard core diameter. For high packing fractions at which ρσ3≳0.93, the experimental fluidity is much larger than the theoretically predicted fluidity. This observation suggests a possible density effect on the effective hard core diameter at very high densities. In addition, the experimental hard core diameters are compared with the diameters obtained by other techniques.