Liquid–vapor criticality in a fluid of charged hard dumbbells

Abstract

The vapor–liquid criticality of a fluid of charged hard dumbbells is investigated employing grand canonical Monte Carlo simulations and mixed-field finite-size scaling methods. The reduced critical temperature and density obtained are Tc*=0.04911±0.00003 and ρc*=0.101±0.003, respectively. The critical temperature is very close to that of the restricted primitive model (RPM) for ionic fluids, while the critical density is ∼25% larger than that of the RPM. The “fits” to the Ising ordering operator distribution are good, and are of similar quality to those found for the RPM with systems of comparable size. However, for the finite-size systems simulated, the constant volume heat capacity, CV, gives no indication of an Ising-type “divergence” at Tc. This is analogous to the RPM, and serves to demonstrate that this still puzzling behavior is not restricted to that model.