It is proposed to consider the contribution of the nonisolated molecular pairs to the configurational Helmholtz energy, i.e., the quantityfast;/RTminus;Brgr;, where the product of the second virial coefficientBtimes molar density rgr; covers the contribution of the isolated pairs. Especially illuminating is the difference function Dgr; = (fast;/RTminus;Brgr;)realthinsp;thinsp;fluidminus;(fast;/RTminus;Brgr;)hardthinsp;thinsp;bodythinsp;thinsp;fluid. From the few examples given it seems that this difference function is of a general nature provided that the anisotropy of the hard bodies corrsponds to the anisotropy of the molecules of the real fluid. The difference function can be correlated empirically in a simple way and can be used for estimating thermodynamic properties at intermediate and low densities from high density results.
展开▼
