Statistical mechanical modeling of associating solutions

One major obstacle in the development of statistical mechanical models for associating fluids and fluid mixtures has been the lack of accurate intermolecular potential models for such systems. One theory which has shown to be promising in solving this problem without the need for intermolecular potential function is the fluctuation theory of mixtures. This paper consists of recent work of the authors on the development of a new fluctuation theory approaches for calculation of total, partial molar properties, and phase equilibria of associating fluid mixtures. This technique is based upon the newly developed exact relations among the mixture direct correlation function integrals and the closures for unlike-interaction direct correlation function integrals. A new closure for unlike-interaction direct correlation function integrals is suggested and the effect of pressure on the coefficients of two closures is studied.