Phase diagrams of polydisperse van der Waals fluids

The phase behavior of a system composed of spherical particles with a monom odal size distribution is investigated theoretically within the context of the van der Waals approximation for polydisperse fluids. It is shown how th e binodals, spinodals, cloud-point and shadow curves as well as all the (po lydispersity induced) critical points can be obtained for a variety of inte raction potentials. The polydispersity induced modifications of the phase d iagram (even for a polydispersity index I as small as I approximate to1.01) should be observable in some colloidal dispersions. (C) 2000 American Inst itute of Physics. [S0021-9606(00)51842-X].