Phase behavior of a simple model of ferrocolloidal fluid

We propose a simple model of ferrocolloidal fluid and study its phase behavior. The model consists of a two-component mixture of highly asymmetric charged hard spheres with the smaller hard spheres representing counterions, and the larger hard spheres, which represent the polyions, possessing both charge and a magnetic dipole moment. The liquid–gas phase behavior is studied at different values of the charge asymmetry using thermodynamic perturbation theory for associating fluids with central force associative potential. Upon increasing the counterion to polyion charge ratio the critical temperature and density exhibit nonmonotonic behavior, which is governed by the competition between dipole–dipole and charge–charge interactions.