THE PRIMITIVE MODEL OF IONIC FLUIDS NEAR ITS CRITICAL-POINT IN THE POISSON-BOLTZMANN AND MODIFIED POISSON-BOLTZMANN THEORIES

The Poisson-Boltzmann (PB) and modified Poisson-Boltzmann (MPB) theories are used to investigate the primitive model of ionic fluids in the low density-large coupling regime where the liquid-vapor transition is situated. The PB and MPB spinodal curves for the restricted primitive model are calculated from the virial route and compared with those from the mean spherical approximation (energy route) and the hybrid hypernetted-chain/mean spherical approximation (virial route). The effect of unequal ion sizes on the critical point and spinodal curves is also considered.