Critical parameters of the restricted primitive model

The critical parameters for the restricted primitive model of electrolyte solutions were determined from extensive grand canonical Monte Carlo simulations combined with mixed-field finite-size scaling. The fine-lattice discretization method was used for the calculations, with Ewald summation of the long-range coulombic forces. Ising criticality and no pressure mixing were assumed in the finite-size scaling analysis. The critical parameters were obtained as a function of boundary conditions at infinite distance (ε∞), system size L, and lattice discretization parameter ζ. They were found to be sensitive to L for vacuum boundary conditions (ε∞=1), but much less so for “tin-foil” boundary conditions (ε∞=∞). The critical temperature and density decrease with increasing ζ. These calculations are compared to previous estimates of the critical parameters for this model. Extrapolation of our results to the thermodynamic limit in continuous space (L→∞ and ζ→∞) yields Tc*=0.0489±0.0003, ρc*=0.076±0.003.