Phase behavior of the Widom-Rowlinson mixture

The Widom-Rowlinson mixture is a two component fluid where like species do not interact and unlike species interact via a hard core repulsion. As the density is increased this fluid phase separates. Using semigrand ensemble simulations and finite size scaling we accurately locate the critical density at rho sigma(3) = 0.762 +/- 0.016 where rho is the total number density and sigma is the hard sphere diameter. This density is much higher than previous estimates for this model. We implement several integral equation theories, none of which are accurate for the critical point or coexistence curve. (C) 1996 American Institute of Physics.