The generalized van der waals partition function. V. Mixture of square-well fluids of different sizes and energies

Abstract

In this communication we report the results of Monte Carlo simulations for mixtures of square-well molecules of different sizes and interaction energies. We use these results to test various local composition models which have been suggested, and find that only the model proposed earlier is in reasonable agreement with the simulations. This local composition model is then used in the generalized van der Waals partition function to derive a new density-dependent equation of state mixing rule. This mixing rule increases the order of the volume dependence of any equation to which it is applied, though a simple modification to the solution algorithm proposed here easily handles this problem. We find that this new density-dependent mixing rule leads to more accurate predictions than the van der Waals one-fluid mixing rule when no binary interaction parameters are used, and retains only the advantage of smaller values of these parameters and slightly better critical region predictions when binary interaction parameters are used.