Individual activity coefficients of a solvent primitive model electrolyte calculated from the inverse grand-canonical Monte Carlo simulation and MSA theory

Abstract

The recently developed inverse grand-canonical Monte Carlo technique (IGCMC) (S. Lamperski. Molecular Simulation 33, 1193 (2007)) and the MSA theory are applied to calculate the individual activity coefficients of ions and solvent for a solvent primitive model (SPM) electrolyte. In the SPM electrolyte model the anions, cations and solvent molecules are represented by hard spheres immersed in a dielectric continuum whose permittivity is equal to that of the solvent. The ions have a point electric charge embedded at the centre. A simple 1:1 aqueous electrolyte is considered. The ions are hydrated while the water molecules form clusters modelled by hard spheres of diameter d _s. The diameter d _s depends on the dissolved salt and is determined by fitting the mean activity coefficient ln γ _± calculated from IGCMC and from the MSA to the experimental data. A linear correlation is observed between d _s and the Marcus parameter ΔG _HB, which describes the ion influence on the water association.

Keywords:

• ionic activity coefficient
• solvent primitive model
• inverse grand-canonical Monte Carlo technique
• Marcus parameter

Acknowledgement

Financial support from Adam Mickiewicz University, Faculty of Chemistry, is appreciated.