Simulation studies of shear viscosity time-correlation-functions

Abstract

Computer simulations of the Green–Kubo time‐correlation‐functions (tcfs) for the shear viscosity are reported for argon (Lennard‐Jonesium) at several state points. The principal function of interest is the contribution that involves the intermolecular forces. This particular tcf is the sum of a two‐body, a three‐body, and a four‐body term. The time‐dependencies and magnitudes of these individual tcfs have been evaluated over a wide range of density at 151 K and for a single state point near the argon triple point. It is shown that all of these component tcfs are significant; that their time‐dependencies at moderately short times are quite different from one another; and that the individual functions display pronounced long‐time‐tails at high density. However, a tail does not appear in the total tcf because of cancellation in the summation. That is, the long‐time‐tails appear in the partial tcfs in the ratio 2‐body:3‐body:4‐body=1:−2:1.