Monte Carlo simulation of the nonadditive restricted primitive model of ionic fluids: Phase diagram and clustering

摘要

We report an accurate Monte Carlo calculation of the phase diagram and clustering properties of the restrictednprimitive model with nonadditive hard-sphere diameters. At high density the positively nonadditive fluid showsnmore clustering than in the additive model and the negatively nonadditive fluid shows less clustering than in thenadditive model; at low density the reverse scenario appears. A negative nonadditivity tends to favor the formationnof neutrally charged clusters starting from the dipole. A positive nonadditivity favors the pairing of like ions atnhigh density. The critical point of the gas-liquid phase transitionmoves at higher temperatures and higher densitiesnfor a negative nonadditivity and at lower temperatures and lower densities for a positive nonadditivity. The lawnof corresponding states does not seem to hold strictly. Our results can be used to interpret recent experimentalnworks on room temperature ionic liquids.