NETWORK FORMING FLUIDS - INTEGRAL-EQUATIONS AND MONTE-CARLO SIMULATIONS

A network forming four-site model associative fluid (with freely locat ed sites) is investigated by means of associative Ornstein-Zernike int egral equation theory supplemented by a Percus-Yevick-like closure rel ation. Since the model exhibits critical behavior, the structure relev ant to the gaseous and to the liquid phases are discussed. The propert ies of network forming systems with different strengths of the site-si te attraction are analyzed. This allows us to describe topologically a symmetrical network clusters and branching polymers. It is determined that the critical temperature as well as the critical density become l ower with an increasing degree of asymmetry. NVT Monte Carlo simulatio ns for the same model, but with a fixed location of sites, are present ed. Theoretical predictions are compared to the simulation results. It is shown that the theory agrees well with the simulations, except for low densities and temperatures, where the simulations predict a well developed waterlike structure with a tetrahedral arrangement. This dis agreement is shown to be caused by the difference in the site location imposed by the model potentials. (C) 1998 American Institute of Physi cs. [S0021-9606(98)50621-6].