A simple mixture model based on the mixture pair correlation functions
was developed and tested. For a Lennard-Jones fluid, the new model sh
owed high accuracy when compared to simulation data. The model was com
pared to the van der Waals model, the dense fluid theory model and the
more complex perturbation model of Weeks-Chandler-Anderson, Lee-Leves
que and Grundke-Henderson (WCA-LL-GH); it showed a comparable accuracy
to the latter. For hard sphere molecules, the model predictions are c
omparable to the accurate Mansoori-Carnahan-Starling-Leland equation f
or mixtures of hard spheres. However, at high densities, an abnormal b
ehavior was observed for small concentrations of the larger component,
when the model is used with the Carnahan-Starling equation of state f
or the pure hard spheres. This might point to phase separation or to a
limitation of the new model under the conditions studied. A procedure
for extending the model to non-spherical and polar molecules is sugge
sted.