Phase Equilibria of Size-Asymmetric Primitive Model Electrolytes

The low-temperature phase coexistence of size-asymmetric primitive model electrolyte solutions has been investigated by means of Monte Carlo simulations. Binodal curves and critical parameters are reported as a function of size ratio $\lambda ={\sigma }_{+}/{\sigma }_{-}$ in the range 0.05 to 1. Both the critical temperature and the critical density are found to decrease as $\lambda$ decreases. These trends are in conflict with available theoretical predictions. For highly asymmetric systems, the depression of the critical parameters is accompanied by the formation of large chainlike and ringlike structures, thereby giving rise to considerable finite-size effects.