TIME-CORRELATION FUNCTIONS OF CLASSICAL FLUIDS - A SELF-CONSISTENT APPROACH

The hierarchy of the Mori-Zwanzing continued fraction representation h as been studied by expressing the memory function in terms of its lowe r-order memory function. The short-time behavior of the memory functio n is exactly incorporated through sum rules by scaling its lower-order memory function. This scheme provides a self-consistent evaluation of the memory function and hence of the time correlation function. Expre ssions obtained for transport coefficients have been found to be exact ly the same as those obtained by Joslin and Gray [Mel. Phys. 58, 789 ( 1986)]. The approach has been applied to study the velocity autocorrel ation function of the Lennard-Jones fluids and a good agreement with m olecular dynamics data is obtained for dense fluids.