Extraction of transport coefficients from correlation functions

In this paper we apply a new method to the calculation of transport coefficients by computer simulation of fluids. It differs from previous methods in two essential respects. Firstly, it involves the simultaneous fitting of all of the correlations among conserved hydrodynamic variables, rather than just the density or current autocorrelation function. This gives more detailed information on the hydrodynamics, and, in particular, makes it possible to separate some of the effects of viscoelasticity, which may seriously bias transport-coefficient estimates. Secondly, it is formulated in a simple way, which avoids certain complicating approximations traditionally made in computing fluid correlation functions. Results of pilot calculations for the soft-sphere viscosity agree with those of previous workers. The most conspicuous physical effect observed is a strong wave-vector dependence of the thermal diffusivity, in agreement with previous work.