Equilibrium properties of charged hard spheres of different diameters in the electrolyte solution regime: Monte Carlo and integral equation results

Abstract

Extensive Monte Carlo (MC) and integral equation calculations of thermodynamic and structural properties for the 1-1 aqueous electrolyte regime of the primitive model are reported. The salt concentration covers the range 0.1–2 M. The ratio of the radii of the two ionic species α covers the range 0.1–0.8. The MC results are compared to the results of the HNC, MSA, and EXP approximations. The excess internal energies calculated in the HNC are found to be in good agreement with the MC values. In the MSA the energy turns out to be too high for large α and too small for small α. For α=0.4 the MSA value is accurate as compared to the simulation. Similar remarks hold for the osmotic coefficient. The radial distribution functions (RDF) calculated in the EXP approximation agree fairly well with the MC results at all molarities and radius ratios investigated, except for α=0.1, where the agreement is only qualitative. The MSA yields RDF which are in qualitative agreement with the MC only at high concentrations and for not too small α. Some preliminary MC results are also reported for the 2-2 aqueous electrolyte solutions at 2 M with α=0.4. An enhancement occurs in the peak of g++(r) and g−−(r) with respect to the peak of the corresponding glike(r) of the 2-2 symmetrical case (α=1). This peak is commonly associated with ion clustering. It appears that this effect is more pronounced for ions of different diameters.

Effective interactions in the colloidal suspensions from hypernetted-chain theory

“…In the literature, detailed comparisons of the two-body correlation functions and thermodynamic properties computed from the HNC theory and Monte-Carlo simulations have been made for ionic solutions [16,17,18,19,20,21,22,23]. They have defined the domain of validity of the HNC approximation for ionic concentrations ≃ 1 M and charge and size ratios of the order of 1-20.…”

Renormalized charge in a two-dimensional model of colloidal suspension from hypernetted chain approach

“…Specifically, for ionic solutions, there has been detailed comparisons between HNC theory and Monte Carlo simulations, [20][21][22][23][24][25] showing that the HNC closure provides excellent accuracy for the correlation functions, specially at large distances. Specifically, for ionic solutions, there has been detailed comparisons between HNC theory and Monte Carlo simulations, [20][21][22][23][24][25] showing that the HNC closure provides excellent accuracy for the correlation functions, specially at large distances.…”

“…[3][4][5][6][7][8][9][10][11] In the mean-field approach, the renormalized charge is an increasing function of the bare charge. 13,14 The HNC closure is known to give very good accuracy for charged systems [20][21][22][23][24][25] for a wide range of parameters: concentrations up to 1M and charge and size asymmetry ratios up to 20 ͑for larger parameters the HNC numerical algorithm can present lack of convergence͒. However, the mean-field approach has limitations, specially for multivalent ions, because of the increase of the Coulomb coupling.…”

A new three-particle-interaction model to predict the thermodynamic properties of different electrolytes

“…On the other hand, the mean spherical approximation (MSA) is showing up as a powerful tool for calculating the thermodynamic properties of electrolytes in the primitive model [22,23]. Lu et al [24] improved the primitive MSA and successfully calculated the activity coefficients of electrolytes across the wide range of concentration.…”