Bridging atomistic simulations and thermodynamic hydration models of aqueous electrolyte solutions

Wang, Xiangwen, Clegg, Simon L. and Di Tommaso, Devis (2022) Bridging atomistic simulations and thermodynamic hydration models of aqueous electrolyte solutions. The Journal of Chemical Physics, 156 (2). ISSN 0021-9606

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Chemical thermodynamic models of solvent and solute activities predict the equilibrium behavior of aqueous solutions. However, these models are semi-empirical. They represent micro-scale ion and solvent behaviors controlling the macroscopic properties using small numbers of parameters whose values are obtained by fitting to activities and other partial derivatives of the Gibbs energy measured for the bulk solutions. We have conducted atomistic simulations of aqueous electrolyte solutions (MgCl2 and CaCl2) to determine the parameters of thermodynamic hydration models. We have implemented a cooperative hydration model to categorize the water molecules in electrolyte solutions into different subpopulations. The value of the electrolyte-specific parameter, k, was determined from the ion-affected subpopulation with the lowest absolute value of the free energy of removing the water molecule. The other equilibrium constant parameter, K1, associated with the first degree of hydration, was computed from the free energy of hydration of hydrated clusters. The hydration number, h, was determined from a reorientation dynamic analysis of the water subpopulations compared to bulk-like behavior. The reparameterized models [R. H. Stokes and R. H. Robinson, J. Solution Chem. 2, 173 (1973) and Balomenos et al., Fluid Phase Equilib. 243, 29 (2006)] using the computed values of the parameters lead to the osmotic coefficients of MgCl2 solutions that are consistent with measurements. Such an approach removes the dependence on the availability of experimental data and could lead to aqueous thermodynamic models capable of estimating the values of solute and solvent activities as well as thermal and volumetric properties for a wide range of compositions and concentrations.

Item Type: Article
Additional Information: Acknowledgements: X.W. acknowledges the QMUL Principal’s Studentship for funding. D.D.T. acknowledges the ACT programme (Accelerating CCS Technologies, Horizon2020 Project No. 294766), which funded the FUNMIN project. Financial contributions were made from the Department for Business, Energy & Industrial Strategy (BEIS) together with extra funding from the NERC and EPSRC research councils (United Kingdom), ADEME (FR), and MINECO-AEI (ES). We thank the UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by the EPSRC No. (EP/P020194/1). Through our membership of the UK’s HEC Materials Chemistry Consortium, which is funded by the EPSRC No. (EP/L000202), this work used the ARCHER UK National Supercomputing Service ( This research utilized Queen Mary’s Apocrita HPC facility, supported by QMUL Research-IT (
Uncontrolled Keywords: physics and astronomy(all),physical and theoretical chemistry ,/dk/atira/pure/subjectarea/asjc/3100
Faculty \ School: Faculty of Science > School of Environmental Sciences
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Depositing User: LivePure Connector
Date Deposited: 17 Feb 2022 13:30
Last Modified: 13 Jan 2023 01:38
DOI: 10.1063/5.0074970


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