Multibody distribution function contributions to the heat capacity for the truncated Lennard-Jones fluid

Abstract

We have performed a series of standard NVT Monte Carlo simulations in which we have calculated the configurational heat capacity, Cv, of a truncated Lennard-Jones model fluid by the fluctuation theorem. As we found in a previous investigation, the heat capacity exhibited two extrema as a function of density on sufficiently low temperature isotherms. During the course of these runs, we have decomposed the heat capacity into the sum of quantities, Cv(2), Cv(3), and Cv(4), which are averages over two, three, and four body distribution functions. We analyze combinations of the three contributions to gain insight into the nature of the extrema. In particular, we find that the sum Cv(2)+Cv(3) has a maximum and a minimum at all temperatures studied. The magnitude and slope of Cv(2)+Cv(3) compared with Cv(4) determines whether or not Cv itself has maxima and minima.