Recent Progress in Molecular Simulation of Aqueous Electrolytes: Force Fields, Chemical Potentials and Solubility

Abstract

Although aqueous electrolytes are among the most important solutions, the molecular simulation of their intertwined properties of chemical potentials, solubility and activity coefficients has remained a challenging problem, and has attracted considerable recent interest. In this perspectives review, we focus on the simplest case of aqueous sodium chloride at ambient conditions and discuss the two main factors that have impeded progress. The first is lack of consensus with respect to the appropriate methodology for force field (FF) development. We examine how most commonly used FFs have been developed, and emphasize the importance of distinguishing between "Training Set Properties" used to fit the FF parameters, and "Test Set Properties", which are pure predictions of additional properties. The second is disagreement among solubility results obtained, even using identical FFs and thermodynamic conditions. Solubility calculations have been approached using both thermodynamic--based methods and direct molecular dynamics--based methods implementing coexisting solution and solid phases. Although convergence has been very recently achieved among results based on the former approach, there is as yet no general agreement with simulation results based on the latter methodology. We also propose a new method to directly calculate the electrolyte standard chemical potential in the Henry-Law ideality model. We conclude by making recommendations for calculating solubility, chemical potentials and activity coefficients, and outline a potential path for future progress.

arXiv comment32 pages and 12 figures. Accepted by Molecular Physics, 08 Mar. 2016

References in corpus (6)

• An efficient, multiple range random walk algorithm to calculate the density of states
• Dynamical Fluctuating Charge Force Fields: Application to Liquid Water
• Finite-size corrections to the free energy of crystalline solids
• Polarizable Mean-Field Model of Water for Biological Simulations with Amber and Charmm force fields
• Crystal lattice properties fully determine short-range interaction parameters for alkali and halide ions
• Ionic force field optimization based on single-ion and ion-pair solvation properties

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