The heat capacity of the restricted primitive model electrolyte

The constant-volume heat capacity, CV(T ,r), of the restricted primitive model ~RPM! electrolyte is considered in the vicinity of its critical point. It is demonstrated that, despite claims, recent simulations for finite systems do not convincingly indicate the absence of a divergence in CV(T ,r)—which would point to non-Ising-type criticality. The strong qualitative difference between CV for the RPM and for a Lennard-Jones fluid is shown to result from the low critical density of the former. If one considers the theoretically preferable configurational heat-capacity density, CV /V , the finite-size results for the two systems display qualitatively similar behavior on near-critical isotherms. © 2001 American Institute of Physics. @DOI: 10.1063/1.1359769#