On the number dependence of viscosity in three dimensional fluids

We compute the shear viscosity of three dimensional simple fluids using nonequilibrium molecular dynamics. We show that for systems of 256 particles or more, the shear viscosity is, within ½ per cent, independent of the number of particles used in the simulation. We estimate that the zero shear rate viscosity of the triple point Lennard-Jones fluid is 3·41 ± 0·07. We observe small, but statistically significant departures from the square root dependence of viscosity with respect to shear rate. We show that by truncating the Lennard-Jones potential at 2·5σ, changes the viscosity by no more than ∼½ per cent compared to the untruncated fluid.