Electrical double layers and differential capacitance in molten salts from density functional theory

Frischknecht, Amalie L.; Halligan, Deaglan O.; Parks, Michael L.

doi:10.1063/1.4891368

Cited by 30 publications

(19 citation statements)

References 40 publications

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“…To address the limitations of the GC theory, various advanced theories have been developed, such as the modified PB theory, 10 integral equation theory, 11 and classical density functional theory (cDFT). [12][13][14][15][16][17] These theories, in addition to the electrostatic interactions, mainly account for the finite size effects of ions and van der Waals interactions among them. However, they usually ignore molecular details of water and variations in the dielectric permittivity.…”

Section: Introductionmentioning

confidence: 99%

Langevin-Poisson-EQT: A dipolar solvent based quasi-continuum approach for electric double layers

Mashayak

Aluru

2017

The Journal of Chemical Physics

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Water is a highly polar solvent. As a result, electrostatic interactions of interfacial water molecules play a dominant role in determining the distribution of ions in electric double layers (EDLs). Near a surface, an inhomogeneous and anisotropic arrangement of water molecules gives rise to pronounced variations in the electrostatic and hydration energies of ions. Therefore, a detailed description of the structural and dielectric properties of water is important to study EDLs. However, most theoretical models ignore the molecular effects of water and treat water as a background continuum with a uniform dielectric permittivity. Explicit consideration of water polarization and hydration of ions is both theoretically and numerically challenging. In this work, we present an empirical potential-based quasi-continuum theory (EQT) for EDL, which incorporates the polarization and hydration effects of water explicitly. In EQT, water molecules are modeled as Langevin point dipoles and a point dipole based coarse-grained model for water is developed systematically. The space dependence of the dielectric permittivity of water is included in the Poisson equation to compute the electrostatic potential. In addition, to reproduce hydration of ions, ion-water coarse-grained potentials are developed. We demonstrate the EQT framework for EDL by simulating NaCl aqueous electrolyte confined inside slit-like capacitor channels at various ion concentrations and surface charge densities. We show that the ion and water density predictions from EQT agree well with the reference molecular dynamics simulations.

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Section: Introductionmentioning

confidence: 99%

Langevin-Poisson-EQT: A dipolar solvent based quasi-continuum approach for electric double layers

Mashayak

Aluru

2017

The Journal of Chemical Physics

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“…To describe the frequency dependence of the impedance of ionic conductors various theoretical approaches have been proposed [15][16][17][18][19], one being based on solutions of the Poisson-Nernst-Planck (PNP) equations (see, e.g., [3,20,21]). In this approach, it is assumed that under an external electric field ions movement is due to migration and diffusion and is described by the continuity equation.…”

Section: Introductionmentioning

confidence: 99%

Influence of dielectric layers on estimates of diffusion coefficients and concentrations of ions from impedance spectroscopy

Khazimullin

Lebedev

2019

Phys. Rev. E

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We present the analysis of the impedance spectra for a binary electrolyte confined between blocking electrodes with dielectric layers. An expression for the impedance is derived from Poisson-Nernst-Planck equations in the linear approximation taking into account the voltage drop on the dielectric layer. The analysis shows, that characteristic features of the frequency dependence of the impedance are determined by the ratio of the Debay length and the effective thickness of the dielectric layer. The impact of the dielectric layer is especially strong in the case of high concentrated electrolytes, where the Debay length is small and thus comparable to the effective thickness of the dielectric layer. To verify the model, measurements of the impedance spectra and transient currents in a liquid crystal 4-n-pentyl-4'-cyanobiphenyl (5CB) confined between polymercoated electrodes in cells of different thicknesses are performed. The estimates for the diffusion coefficient and ion concentration in 5CB obtained from the analysis of the impedance spectra and the transient currents are consistent and agree with previously reported data. We demonstrate that calculations of the ion parameters from the impedance spectra without taking into account the dielectric layer contribution lead in most cases to incorrect results. Application of the model to analyze violations of the low-frequency impedance scaling and contradictions in the estimates of the ion parameters recently found in some ionic electrolytes are discussed. * maxim@anrb.ru arXiv:1804.04843v1 [cond-mat.soft]

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“…There exist liquid state theories, such as the modified PB theory, 22 integral equation theory, 23 and classical density functional theory (cDFT). [24][25][26][27][28][29] These theories, in addition to the electrostatic interactions, mainly account for the finite size effects of ions and van der Waals interactions among them. However, they usually ignore molecular details of water and variations in the dielectric permittivity.…”

Section: Introductionmentioning

confidence: 99%

A multiscale model for charge inversion in electric double layers

Mashayak

Aluru

2018

The Journal of Chemical Physics

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Charge inversion is a widely observed phenomenon. It is a result of the rich statistical mechanics of the molecular interactions between ions, solvent, and charged surfaces near electric double layers (EDLs). Electrostatic correlations between ions and hydration interactions between ions and water molecules play a dominant role in determining the distribution of ions in EDLs. Due to highly polar nature of water, near a surface, an inhomogeneous and anisotropic arrangement of water molecules gives rise to pronounced variations in the electrostatic and hydration energies of ions. Classical continuum theories fail to accurately describe electrostatic correlations and molecular effects of water in EDLs. In this work, we present an empirical potential based quasi-continuum theory (EQT) to accurately predict the molecular-level properties of aqueous electrolytes. In EQT, we employ rigorous statistical mechanics tools to incorporate interatomic interactions, long-range electrostatics, correlations, and orientation polarization effects at a continuum-level. Explicit consideration of atomic interactions of water molecules is both theoretically and numerically challenging. We develop a systematic coarse-graining approach to coarse-grain interactions of water molecules and electrolyte ions from a high-resolution atomistic scale to the continuum scale. To demonstrate the ability of EQT to incorporate the water orientation polarization, ion hydration, and electrostatic correlations effects, we simulate confined KCl aqueous electrolyte and show that EQT can accurately predict the distribution of ions in a thin EDL and also predict the complex phenomenon of charge inversion.

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Electrical double layers and differential capacitance in molten salts from density functional theory

Cited by 30 publications

References 40 publications

Langevin-Poisson-EQT: A dipolar solvent based quasi-continuum approach for electric double layers

Langevin-Poisson-EQT: A dipolar solvent based quasi-continuum approach for electric double layers

Influence of dielectric layers on estimates of diffusion coefficients and concentrations of ions from impedance spectroscopy

A multiscale model for charge inversion in electric double layers

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