The heat capacity of the restricted primitive model electrolyte

The constant-volume heat capacity, C-V(T,rho), 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 C-V(T,rho)-which would point to non-Ising-type criticality. The strong qualitative difference between C-V 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, C-V/V, the finite-size results for the two systems display qualitatively similar behavior on near-critical isotherms. (C) 2001 American Institute of Physics.