Ionic fluids: charge and density correlations near gas-liquid criticality

Abstract

The correlation functions of an ionic fluid with charge and size asymmetry are studied within the framework of the random phase approximation. The results obtained for the charge-charge correlation function demonstrate that the second-moment Stillinger-Lovett (SL) rule is satisfied away from the gas-liquid critical point (CP) but not, in general, at the CP. However in the special case of a model without size assymetry the SL rules are satisfied even at the CP. The expressions for the density-density and charge-density correlation functions valid far and close to the CP are obtained explicitely.