INTEGRAL-EQUATION APPROACHES TO MIXTURES OF ATOMIC AND MOLECULAR FLUIDS

A recent extension to mixtures of Verlet's closure is applied in conju nction with the Ornstein-Zernike relation to solve the structure and t hermodynamics of mixtures of hard-spheres and homonuclear hard-dumbbel ls. This integral equation (IE), which is proven to be very accurate w hen compared with simulation data, is used to explore the possibility of phase separation in an asymmetric mixture. While our results do not show evidence of such phase separation in the asymmetric binary hard- sphere mixture studied by Biben and Hansen [T. Biben and J. P. Hansen, Phys. Rev. Lett. 66, 2215 (1991)], an equivalent mixture of hard-dumb bells and large hard-spheres seems to exhibit a certain tendency to ph ase separate as far as the integral equation results are concerned. Fi nally, given the ability of this integral equation to reproduce the ha rd-core system, we have incorporated these results into a previous Ref erence Hypernetted Chain scheme to treat a mixture of N-2 and Ar model ed by means of site-site Lennard-Jones potentials. In consonance with the results for pure fluids, the parameterization of a hard-core refer ence system with the same molecular shape leads to excellent results b oth for the structure and thermodynamics of real systems. (C) 1997 Ame rican Institute of Physics.