  In this paper, we present a cluster algorithm for the numerical simulations
of non-additive hard-core mixtures. This algorithm allows one to simulate and
equilibrate systems with a number of particles two orders of magnitude larger
than previous simulations. The phase separation for symmetric binary mixtures
is studied for different non-additvities as well as for the Widom-Rowlinson
model (B. Widom and J. S. Rowlinson, J. Chem. Phys. 52, 1670 (1970)) in two and
three dimensions. The critical densities are determined from finite size
scaling. The critical exponents for all the non-additivities are consistent
with the Ising universality class.
