We present a density functional theory for the m-component Widom-Rowlinson model, for a mixture of spherical particles where the unlike species interact with a hard-core potential and the interactions between like species vanish. The functional is exact for small densities and in the zero-dimensional limit. It predicts the fluid structure in good agreement with simulations and yields a continuous demixing phase transition for $m=2.\mathrm{}$ In the limit of large m the Widom-Rowlinson model reduces to effective hard spheres in the mixed phase and the Asakura-Oosawa (colloid-ideal polymer) model in the demixed phase. Within the present theory, both cases are captured correctly. For intermediate m we find a first order demixing phase transition, with a rapidly broadening density discontinuity upon increasing m.

• Received 8 August 2000

DOI:https://doi.org/10.1103/PhysRevE.63.010101