From Solvent-Free to Dilute Electrolytes: Essential Components for a Continuum Theory

Gavish, Nir; Elad, Doron; Yochelis, Arik

doi:10.1021/acs.jpclett.7b03048

Cited by 70 publications

(107 citation statements)

References 68 publications

(254 reference statements)

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“…Such oscillations were predicted much earlier by Kirkwood [12], and the crossover at the onset of oscillations is known as the Kirkwood line. We note that charge oscillations emerge also from several Ginzburg-Landau-type theories that are used, for example, to describe the charge density of ionic liquids in the proximity of charged surfaces [28][29][30][31][32][33].…”

Section: Introductionmentioning

confidence: 94%

Screening length for finite-size ions in concentrated electrolytes

et al. 2019

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The classical Debye-Hückel (DH) theory clearly accounts for the origin of screening in electrolyte solutions and works rather well for dilute electrolyte solutions. While the Debye screening length decreases with the ion concentration and is independent of ion size, recent surface-force measurements imply that for concentrated solutions, the screening length exhibits an opposite trend; it increases with ion concentration and depends on the ionic size. The screening length is usually defined by the response of the electrolyte solution to a test charge, but can equivalently be derived from the charge-charge correlation function. By going beyond DH theory, we predict the effects of ion size on the charge-charge correlation function. A simple modification of the Coulomb interaction kernel to account for the excluded volume of neighboring ions yields a non-monotonic dependence of the screening length (correlation length) on the ionic concentration, as well as damped charge oscillations for high concentrations.

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Section: Introductionmentioning

confidence: 94%

Screening length for finite-size ions in concentrated electrolytes

et al. 2019

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“…Recently, Gavish et al [42] and Rotenberg et al [43] suggested alternative theoretical explanations of the underscreening effect. Their arguments were based, respectively, on the phenomenological density-functional approach and the mean-spherical approximation.…”

Section: Nature Of Compacity and Overscreening Vs Underscreeningmentioning

confidence: 99%

Free and Bound States of Ions in Ionic Liquids, Conductivity, and Underscreening Paradox

et al. 2019

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Using molecular dynamics simulations and theoretical analysis of velocity-autocorrelation functions, we study ion transport mechanisms in typical room-temperature ionic liquids. We show that ions may reside in two states: free and bound with an interstate exchange. We investigate quantitatively the exchange process and reveal new qualitative features of this process. To this end, we propose a dynamic criterion for free and bound ions based on the ion trajectory density and demonstrate that this criterion is consistent with a static one based on interionic distances. Analyzing the trajectories of individual cations and anions, we estimate the time that ions spend in bound "clustered states" and when they move quasifreely. Using this method, we evaluate the average portion of "free" ions as approximately 15%-25%, increasing with temperature in the range of 300-600 K. The ion diffusion coefficients and conductivities as a function of the temperature calculated from the velocity and electrical-current autocorrelation functions reproduce the reported experimental data very well. The experimental data for the direct-current conductivity (constant ionic current) is in good agreement with theoretical predictions of the Nernst-Einstein equation based on the concentrations and diffusion coefficients of free ions obtained in our simulations. In analogy with electronic semiconductors, we scrutinize an "ionic semiconductor" model for ionic liquids, with valence and conduction "bands" for ions separated by an energy gap. The obtained band gap for the ionic liquid is small, around 26 meV, allowing for easy interchange between the two dynamic states. Moreover, we discuss the underscreening paradox in the context of the amount of free charge carriers, showing that the obtained results do not yet approve its simplistic resolution.

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“…The monotonic decay is captured with mean-field theories [12,67]. While the oscillating component could be interpreted as ion pair orientation [87]. Hence, from introducing spectating ions, which represent ion pairs and neutral aggregates, we can include some effects of strongly correlated systems [13][14][15][16]87].…”

Section: Basic Equations and Conceptsmentioning

confidence: 99%