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Rezaei M, Sakong S, Groß A. Molecular Modeling of Water-in-Salt Electrolytes: A Comprehensive Analysis of Polarization Effects and Force Field Parameters in Molecular Dynamics Simulations. J Chem Theory Comput 2023; 19:5712-5730. [PMID: 37528639 DOI: 10.1021/acs.jctc.3c00171] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/03/2023]
Abstract
Accurate modeling of highly concentrated aqueous solutions, such as water-in-salt (WiS) electrolytes in battery applications, requires proper consideration of polarization contributions to atomic interactions. Within the force field molecular dynamics (MD) simulations, the atomic polarization can be accounted for at various levels. Nonpolarizable force fields implicitly account for polarization effects by incorporating them into their van der Waals interaction parameters. They can additionally mimic electron polarization within a mean-field approximation through ionic charge scaling. Alternatively, explicit polarization description methods, such as the Drude oscillator model, can be selectively applied to either a subset of polarizable atoms or all polarizable atoms to enhance simulation accuracy. The trade-off between simulation accuracy and computational efficiency highlights the importance of determining an optimal level of accounting for atomic polarization. In this study, we analyze different approaches to include polarization effects in MD simulations of WiS electrolytes, with an example of a Na-OTF solution. These approaches range from a nonpolarizable to a fully polarizable force field. After careful examination of computational costs, simulation stability, and feasibility of controlling the electrolyte properties, we identify an efficient combination of force fields: the Drude polarizable force field for salt ions and non-polarizable models for water. This cost-effective combination is sufficiently flexible to reproduce a broad range of electrolyte properties, while ensuring simulation stability over a relatively wide range of force field parameters. Furthermore, we conduct a thorough evaluation of the influence of various force field parameters on both the simulation results and technical requirements, with the aim of establishing a general framework for force field optimization and facilitating parametrization of similar systems.
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Affiliation(s)
- Majid Rezaei
- Institute of Theoretical Chemistry, Ulm University, Oberberghof 7, 89081 Ulm, Germany
| | - Sung Sakong
- Institute of Theoretical Chemistry, Ulm University, Oberberghof 7, 89081 Ulm, Germany
| | - Axel Groß
- Institute of Theoretical Chemistry, Ulm University, Oberberghof 7, 89081 Ulm, Germany
- Helmholtz Institute Ulm (HIU) for Electrochemical Energy Storage, Helmholtzstraße 11, 89069 Ulm, Germany
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Li M, Lv L, Fang T, Hao L, Li S, Dong S, Wu Y, Dong X, Liu H. Self-Consistent Implementation of a Solvation Free Energy Framework to Predict the Salt Solubilities of Six Alkali Halides. J Chem Theory Comput 2023; 19:5586-5601. [PMID: 37471389 DOI: 10.1021/acs.jctc.3c00083] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/22/2023]
Abstract
To assess the salt solubilities of six alkali halides in aqueous systems, we proposed a thermodynamic cycle and an efficient molecular modeling methodology. The Gibbs free energy changes for vaporization, dissociation, and dissolution were calculated using the experimental data of ionic thermodynamic properties obtained from the NBS tables. Additionally, the Marcus' and Tissandier's solvation free energy data for Li+, Na+, K+, Cl-, and Br- ions were compared with the conventional solvation free energies by substituting into our self-consistent thermodynamic cycle. Furthermore, Tissandier's absolute solvation free energy data were used as the training set to refit the Lennard-Jones parameters of OPLS-AA force field for ions. To predict salt solubilities, an assumption of a pseudo-solvent was proposed to characterize the coupling work of a solute with its environment from infinitely diluted to saturated solutions, indicating that the Gibbs energy change of solvation process is a function of ionic strength. Following the self-consistency of the cycle, the newly derived formulas were used to determine the salt solubilities by interpolating the intersection of Gibbs free energy of dissolution and the zero free energy line. The refined ion parameters can also predict the structure and thermodynamic properties of aqueous electrolyte solutions, such as densities, pair correlation functions, hydration numbers, mean activity coefficients, vapor pressures, and the radial dependences of the net charge at 298.15 K and 1 bar. Our method can be used to characterize the solid-liquid equilibria of ions or charged particles in aqueous systems. Furthermore, for highly concentrated strong electrolyte systems, it is essential to introduce accurate water models and polarizable force fields.
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Affiliation(s)
- Miyi Li
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 10081, China
| | - Liqiang Lv
- College of Chemical Engineering, Shijiazhuang University, Hebei, Shijiazhuang 050035, China
| | - Tao Fang
- Beijing Institute of Aerospace Testing Technology, Beijing 100074, China
| | - Long Hao
- Beijing Institute of Aerospace Testing Technology, Beijing 100074, China
| | - Shenhui Li
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 10081, China
| | - Shoulong Dong
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 10081, China
| | - Yufeng Wu
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 10081, China
| | - Xiao Dong
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 10081, China
| | - Helei Liu
- School of Chemistry and Chemical Engineering, Beijing Institute of Technology, Beijing 10081, China
- Key Laboratory of Low-Carbon Conversion Science & Engineering, Shanghai Advanced Research Institute, Chinese Academy of Sciences (Shanghai Advanced Research Institute, Chinese Academy of Sciences), Shanghai 201210, China
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Polarizable force fields for accurate molecular simulations of aqueous solutions of electrolytes, crystalline salts, and solubility: Li+, Na+, K+, Rb+, F−, Cl−, Br−, I−. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2022.119659] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Dočkal J, Lísal M, Moučka F. Molecular dynamics of preferential adsorption in mixed alkali–halide electrolytes at graphene electrodes. J Chem Phys 2022; 157:084704. [DOI: 10.1063/5.0097425] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Understanding the microscopic behavior of aqueous electrolyte solutions in contact with graphene and related carbon surfaces is important in electrochemical technologies, such as capacitive deionization or supercapacitors. In this work, we focus on preferential adsorption of ions in mixed alkali–halide electrolytes containing different fractions of Li+/Na+ or Li+/K+ and/or Na+/K+ cations with Cl− anions dissolved in water. We performed molecular dynamics simulations of the solutions in contact with both neutral and positively and negatively charged graphene surfaces under ambient conditions, using the effectively polarizable force field. The simulations show that large ions are often intuitively attracted to oppositely charged electrodes. In contrast, the adsorption behavior of small ions tends to be counterintuitive. In mixed-cation solutions, one of the cations always supports the adsorption of the other cation, while the other cation weakens the adsorption of the first cation. In mixed-cation solutions containing large and small cations simultaneously, adsorption of the larger cations varies dramatically with the electrode charge in an intuitive way, while adsorption of the smaller cations changes oppositely, i.e., in a counterintuitive way. For (Li/K)Cl mixed-cation solutions, these effects allow the control of Li+ adsorption by varying the electrode charge, whereas, for LiCl single-salt solutions, Li+ adsorption is nearly independent of the electrode charge. We rationalize this cation–cation lever effect as a result of a competition between three driving forces: (i) direct graphene–ion interactions, (ii) the strong tendency of the solutions to saturate the network of non-covalent intermolecular bonds, and (iii) the tendency to suppress local charge accumulation in any region larger than typical interparticle distances. We analyze the driving forces in detail using a general method for intermolecular bonding based on spatial distribution functions and different contributions to the total charge density profiles. The analysis helps to predict whether an ion is more affected by each of the three driving forces, depending on the strength of the ion solvation shells and the compatibility between the contributions of the charge density profiles due to the ion and water molecules. This approach is general and can also be applied to other solutions under different thermodynamic conditions.
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Affiliation(s)
- Jan Dočkal
- Department of Physics, Faculty of Science, Jan Evangelista Purkyně University in Ústí nad Labem, Pasteurova 3544/1, 400 96 Ústí nad Labem, Czech Republic and Department of Molecular and Mesoscopic Modelling, The Czech Academy of Sciences, Institute of Chemical Process Fundamentals, Rozvojová 135/1, Prague, Czech Republic
| | - Martin Lísal
- Department of Physics, Faculty of Science, Jan Evangelista Purkyně University in Ústí nad Labem, Pasteurova 3544/1, 400 96 Ústí nad Labem, Czech Republic and Department of Molecular and Mesoscopic Modelling, The Czech Academy of Sciences, Institute of Chemical Process Fundamentals, Rozvojová 135/1, Prague, Czech Republic
| | - Filip Moučka
- Department of Physics, Faculty of Science, Jan Evangelista Purkyně University in Ústí nad Labem, Pasteurova 3544/1, 400 96 Ústí nad Labem, Czech Republic and Department of Molecular and Mesoscopic Modelling, The Czech Academy of Sciences, Institute of Chemical Process Fundamentals, Rozvojová 135/1, Prague, Czech Republic
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Tran L, Škvára J, Smith WR. Atomistic simulation framework for molten salt vapor–liquid equilibrium prediction and its application to NaCl. J Chem Phys 2022; 156:144501. [DOI: 10.1063/5.0089455] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Knowledge of the vapor–liquid equilibrium (VLE) properties of molten salts is important in the design of thermal energy storage systems for solar power and nuclear energy production applications. The high temperatures involved make their experimental determination problematic, and the development of both macroscopic thermodynamic correlations and predictive molecular-based methodologies are complicated by the requirement to appropriately incorporate the chemically reacting vapor-phase species. We derive a general thermodynamic-based atomistic simulation framework for molten salt VLE prediction and show its application to NaCl. Its input quantities are temperature-dependent ideal-gas free energy data for the vapor phase reactions and density and residual chemical potential data for the liquid. If these are not available experimentally, the former may be predicted using standard electronic structure software, and the latter may be predicted by means of classical atomistic simulation methodology. The framework predicts the temperature dependence of vapor pressure, coexisting phase densities, vapor phase composition, and vaporization enthalpy. It also predicts the concentrations of vapor phase species present in minor amounts (such as the free ions), quantities that are extremely difficult to measure experimentally. We furthermore use the results to obtain an approximation to the complete VLE binodal dome and the critical properties. We verify the framework for molten NaCl, for which experimentally based density and chemical potential data are available in the literature. We then apply it to the analysis of NaCl simulation data for two commonly used atomistic force fields. The framework can be readily extended to molten salt mixtures and to ionic liquids.
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Affiliation(s)
- Leann Tran
- Department of Mathematics and Statistics, University of Guelph, Guelph, Ontario N1G 2W1, Canada
| | - Jiří Škvára
- Institute of Chemical Process Fundamentals, Czech Academy of Sciences, Prague 6, Suchdol, Czech Republic
| | - William R. Smith
- Department of Mathematics and Statistics, University of Guelph, Guelph, Ontario N1G 2W1, Canada
- Department of Chemical Engineering, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada
- Faculty of Science, Ontario Tech University, Oshawa, Ontario L1H 7K4, Canada
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Bianco V, Conde MM, Lamas CP, Noya EG, Sanz E. Phase diagram of the NaCl–water system from computer simulations. J Chem Phys 2022; 156:064505. [DOI: 10.1063/5.0083371] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Affiliation(s)
- V. Bianco
- Departamento de Química Física (Unidad de I+D+i asociada al CSIC), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - M. M. Conde
- Departamento de Ingeniería Química Industrial y Medio Ambiente, Escuela Técnica Superior de Ingenieros Industriales, Universidad Politécnica de Madrid, 28006 Madrid, Spain
| | - C. P. Lamas
- Departamento de Química Física (Unidad de I+D+i asociada al CSIC), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
- Instituto de Química Física Rocasolano, Consejo Superior de Investigaciones Científicas, CSIC, Calle Serrano 119, 28006 Madrid, Spain
| | - E. G. Noya
- Instituto de Química Física Rocasolano, Consejo Superior de Investigaciones Científicas, CSIC, Calle Serrano 119, 28006 Madrid, Spain
| | - E. Sanz
- Departamento de Química Física (Unidad de I+D+i asociada al CSIC), Facultad de Ciencias Químicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
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Hantal G, Kolafa J, Sega M, Jedlovszky P. Single-Particle Dynamics at the Intrinsic Surface of Aqueous Alkali Halide Solutions. J Phys Chem B 2021; 125:665-679. [PMID: 33423500 DOI: 10.1021/acs.jpcb.0c09989] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The distribution of ions in the proximity of the liquid-vapor interface of their aqueous solution has been the subject of an intense debate during the last decade. The effects of ionic polarizability have been one of its salient aspects. Much less has been said about the corresponding dynamical properties, which are substantially unexplored. Here, we investigate the single-particle dynamics at the liquid-vapor interface of several alkali halide solutions, using molecular dynamics simulations with polarizable and nonpolarizable force fields and intrinsic surface analysis. We analyze the diffusion coefficient, residence time, and velocity autocorrelation function of water and ions and investigate how these properties depend on the molecular layer where they reside. While anions are found in the first molecular layer for relatively long times, cations are only making quick excursions into it, thanks to thermal fluctuations. The in-layer residence time of ions and their molar fraction in the layer turned out to be linearly dependent on each other. We interpret this unexpected result using a simple two-state model. In addition, we found that, unlike water and other neat molecular liquids that show a different diffusion mechanism at the surface than in the bulk of their liquid phase, ions do not enjoy enhanced mobility in the surface layer of their aqueous solution. This result indicates that ions in the surface layer are shielded by their nearest water neighbors from being exposed to the vapor phase as much as possible. Such positions are available for the ions at the negatively curved troughs of the molecularly rugged liquid surface.
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Affiliation(s)
- György Hantal
- Institute of Physics and Materials Science, University of Natural Resources and Life Sciences, Peter Jordan Straße 82, Vienna A-1190, Austria
| | - Jiří Kolafa
- Department of Physical Chemistry, University of Chemistry and Technology, Prague CZ-166 28 Prague 6, Czech Republic
| | - Marcello Sega
- Forschungszentrum Jülich GmbH, Helmholtz Institute Erlangen-Nürnberg for Renewable Energy (IEK-11), Fürther Straße 248, Nürnberg D-90429, Germany
| | - Pál Jedlovszky
- Department of Chemistry, Eszterházy Károly University, Leányka utca 6, Eger H-3300, Hungary
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Panagiotopoulos AZ. Simulations of activities, solubilities, transport properties, and nucleation rates for aqueous electrolyte solutions. J Chem Phys 2020; 153:010903. [DOI: 10.1063/5.0012102] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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