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 DAB vanishes as DAB~ξ^-1.26±0.08, where ξ is the correlation length. This is different from renormalization-group and mode coupling theory predictions for model H, which are DAB~ξ^-1.065 and DAB~ξ^-1, respectively.