Charged hard dumbbell in the binding mean-spherical approximation

Abstract

A simple model for charged hard dumbbell is proposed in the binding mean-spherical approximation (BIMSA). The thermodynamic properties are analytical solutions of the unique screening parameter Γ^B with full association. Critical point and vapour-liquid coexistence curve are identical to those of Kalyuzhnyi, Yu. V., 1998, Molec. Phys., 94, 735, where a site-site integral equation has to be solved. Substituting Γ without association for Γ^B, the BIMSA reduces to the simple interpolation scheme (SIS). A simple interpolation between the SIS and the BIMSA is proposed: this gives the critical point (T_c∗ = 0.0525, p∗_c = 0.0640) which, for the time being, is the closest to the computer simulation results. Similarity between the charged hard dumbbell and the restricted primitive model of electrolyte is also addressed.