The radial distribution function in fluid mixtures: Conformal solution theory and molecular dynamics results

Abstract

The conformal solution approach is used to relate the distribution functions g _αβ(r) for a fluid mixture to those of a pure fluid, g _x(r). The procedure is to expand g _αβ(r) about the corresponding function for an ideal solution, using σ _αβ ³ and ε_αβσ_αβ ³ as expansion parameters; the expansion of the function y _αβ(r) is also considered. Molecular dynamics results are reported for the tg _αβ for argon-krypton liquid mixtures using the Lennard-Jones (12, 6) potential. These results are used to test the conformal solution expansions to first order; the g _αβ expansion is found to be superior to that for y _αβ for most r values of interest. The second order term in the conformal solution expansion for the Helmholtz free energy is also calculated for argon-krypton mixtures, and found to be about 10 per cent of the value of A ^E given by the van der Waals 1 theory.