CLOSURES FOR EXACT RELATIONS BETWEEN MIXTURE PAIR CORRELATION INTEGRALS

A new approach for obtaining mixture properties is proposed. It involv es combining recently derived exact equations relating integrals of th e mixture pair correlation functions with approximate closures. A part ial differential equation for the partition function results. This equ ation is integrated using an appropriately selected initial condition. The procedures are illustrated for additive and nonadditive hard sphe res, and new mixture equations are obtained. Comparison with simulatio n data show that the accuracy of the predicted properties depends on t he level of approximation introduced by the closure. Certain mixture e quations gave accurate representation of the equation of state and the phase boundaries of nonadditive hard spheres. In applications where t he structure of the fluid is not needed, the proposed approach is bett er than traditional approaches, because it gives accurate analytical e xpressions for mixture properties and for certain integrals of the pai r correlation functions. (C) 1997 American Institute of Physics. [S002 1-9606(97)50941-X].