Molecular dynamics simulations of a fluid near its critical point

We present computer simulations for the static and dynamic behavior of a fluid near its consolute critical point. We study the Widom-Rowlinson mixture, which is a two component fluid where like species do not interact and unlike species interact via a hard core repulsion. At high enough densities this fluid exhibits a second order demixing transition that is in the Ising universality class. We find that the mutual diffusion coefficient D-AB vanishes as D(AB)similar toxi(-1.26+/-0.08), where xi is the correlation length. This is different from renormalization-group and mode coupling theory predictions for model H, which are D(AB)similar toxi(-1.065) and D(AB)similar toxi(-1), respectively.