On the computation of electrical conductivities of aqueous electrolyte solutions: Two surfaces one property

Blázquez Fernández, Samuel; Fernández Abascal, José Luis; Lagerweij, Jelle; Habibi, Parsa; Dey, Poloumy; Vlugt, Thijs; Moultos, Othonas; Vega De Las Heras, Carlos

On the computation of electrical conductivities of aqueous electrolyte solutions: Two surfaces one property

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Official URL

https://doi.org/10.1021/acs.jctc.3c00562

Publication date

2023

Authors

Blázquez Fernández, Samuel

Fernández Abascal, José Luis

Vega De Las Heras, Carlos

Publisher

American Chemical Society

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URI

https://hdl.handle.net/20.500.14352/88914

Citation

Samuel Blazquez, Jose L. F. Abascal, Jelle Lagerweij, Parsa Habibi, Poulumi Dey, Thijs J. H. Vlugt, Othonas A. Moultos, and Carlos Vega Journal of Chemical Theory and Computation 2023 19 (16), 5380-5393 DOI: 10.1021/acs.jctc.3c00562

Abstract

In this work, we have computed electrical conductivities at ambient conditions of aqueous NaCl and KCl solutions by using the Einstein-Helfand equation. Common force fields (charge q =±1 e) do not reproduce the experimental values of electrical conductivities, viscosities and diffusion coefficients. Recently, we proposed the idea of using different charges to describe the Potential Energy Surface (PES) and the Dipole Moment Surface (DMS). In this work, we implement this concept. The equilibrium trajectories required to evaluate electrical conductivities (within linear response theory) were obtained by using scaled charges (with the value q =±0.75 e) to describe the PES. The potential parameters were those of the Madrid-Transport force field, which describe accurately viscosities and diffusion coefficients of these ionic solutions. However, integer charges were used to compute the conductivities (thus describing the DMS). The basic idea is that although the scaled charge describes the ion-water interaction better, the integer charge reflects the value of the charge that is transported due to the electric field. The agreement obtained with experiments is excellent, as for the first time electrical conductivities (and the other transport properties) of NaCl and KCl electrolyte solutions are described with high accuracy for the whole concentration range up to their solubility limit. Finally, we propose an easy way to obtain a rough estimate of the actual electrical conductivity of the potential model under consideration using the approximate Nernst-Einstein equation, which neglects correlations between different ions.