Person:
Fernández Abascal, José Luis

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First Name
José Luis
Last Name
Fernández Abascal
URI
https://hdl.handle.net/20.500.14352/76142
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Químicas
Department
Area
Química Física
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2022 - 20232
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Author: Blázquez Fernández, Samuel × Item Type: Publication ×

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Now showing 1 - 2 of 2
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    On the computation of electrical conductivities of aqueous electrolyte solutions: Two surfaces one property
    (Journal of Chemical Theory and Computation, 2023) Blázquez Fernández, Samuel; Fernández Abascal, José Luis; Lagerweij, Jelle; Habibi, Parsa; Dey, Poloumy; Vlugt, Thijs; Moultos, Othonas; Vega De Las Heras, Carlos
    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.
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    The Madrid-2019 force field for electrolytes in water using TIP4P/2005 and scaled charges: Extension to the ions F−, Br−, I−, Rb+, and Cs+
    (Journal of Chemical Physics, 2022) Blázquez Fernández, Samuel; Martín Conde, María; Fernández Abascal, José Luis; Vega De Las Heras, Carlos
    In this work, an extension of the Madrid-2019 force field is presented. We have added the cations Rb+ and Cs+ and the anions F−, Br−, and I−. These ions were the remaining alkaline and halogen ions, not previously considered in the Madrid-2019 force field. The force field, denoted as Madrid-2019-Extended, does not include polarizability and uses the TIP4P/2005 model of water and scaled charges for the ions. A charge of ±0.85e is assigned to monovalent ions. The force field developed provides an accurate description of aqueous solution densities over a wide range of concentrations up to the solubility limit of each salt studied. Good predictions of viscosity and diffusion coefficients are obtained for concentrations below 2 m. Structural properties obtained with this force field are also in reasonable agreement with the experiment. The number of contact ion pairs has been controlled to be low so as to avoid precipitation of the system at concentrations close to the experimental solubility limit. A comprehensive comparison of the performance for aqueous solutions of alkaline halides of force fields of electrolytes using scaled and integer charges is now possible. This comparison will help in the future to learn about the benefits and limitations of the use of scaled charges to describe electrolyte solutions.