Molecular Thermodynamics of Size Asymmetrical Charged Hard-dumbbell Fluids

摘要

A molecular thermodynamic model of size asymmetrical charged hard dumbbell fluids is proposed, which consists of two parts: one is the reference electrolyte solution contribution and the other is the positive and negative ions association contribution. For the former we use MSA result of primitive model electrolyte and the latter is a function of the cavity correlation function of the positive and the negative ions. To test the theory, Monte Carlo simulations are performed to calculate the thermodynamic properties at high temperature. We find that if the original MSA solution is used, the variations of thermodynamic properties with the asymmetry of the ions size is qualitatively wrong. If we take the size asymmetrical ions mixtures as symmetrical ones with effective diameter σ_(12) (σ_(12) = (σ_1 + σ_2)/2 is the mean diameter of the positive and negative ions.) not only the formula is greatly simplified but also the agreement between theory and simulation is greatly improved.