Simple theory for oscillatory charge profile in ionic liquids near a charged wall

Ciach, A.

doi:10.1016/j.molliq.2017.10.002

Cited by 22 publications

(15 citation statements)

References 33 publications

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“…3b). Similar it was found in systems with competing interactions [60,61]. This result is expected, since in our model in fact the competing interaction between cations is introduced through the short-range attraction and the electrostatic repulsion on longer distances.…”

Section:  supporting

confidence: 85%

The effect of short-range interaction and correlations on the charge and electric field distribution in a model solid electrolyte

et al. 2019

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A simple lattice model of a solid electrolyte presented as a xy-slab geometry system of mobile cations on a background of energetic landscape of the host system and a compensating field of uniformly distributed anions is studied. The system is confined in the z-direction between two oppositely charged walls, which are in parallel to xy-plane. Besides the long-range Coulomb interactions appearing in the system, the short-range attractive potential between cations is considered in our study. We propose the mean field description of this model and extend it by taking into account correlation effects at short distances. Using the free energy minimization at each of z-coordinates, the corresponding set of non-linear equations for the chemical potential is derived. The set of equations was solved numerically with respect to the charge density distribution in order to calculate the cations distribution profile and the electrostatic potential in the system along z-direction under different conditions. An asymmetry of charge distribution profile with respect to the midplane of the system is observed. The effects of the short-range interactions and pair correlations on the charge and electric field distributions are demonstrated.

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Section:  supporting

confidence: 85%

The effect of short-range interaction and correlations on the charge and electric field distribution in a model solid electrolyte

et al. 2019

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“…The formula (56) fits quite well the simulation results for a particular version of the SALR interactions already for z > 2π/α 1 [44]. The same behavior was predicted for the asymptotic decay of the charge density near a charged wall in ionic systems [50]. In this case, Eq.…”

Section: The Generic Model For Inhomogeneous Systemssupporting

confidence: 77%

Mesoscopic theory for systems with competing interactions near a confining wall

Ciach

2019

Phys. Rev. E

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Mesoscopic theory for self-assembling systems near a planar confining surface is developed. Euler-Lagrange (EL) equations and the boundary conditions (BC) for the local volume fraction and the correlation function are derived from the DFT expression for the grand thermodynamic potential.Various levels of approximation can be considered for the obtained equations. The lowest-order nontrivial approximation (GM) resembles the Landau-Brazovskii type theory for a semiinfinite system. Unlike in the original phenomenological theory, however, all coefficients in our equations and BC are expressed in terms of the interaction potential and the thermodynamic state. Analytical solutions of the linearized equations in GM are presented and discussed on a general level and for a particular example of the double-Yukawa potential. We show exponentially damped oscillations of the volume fraction and the correlation function in the direction perpendicular to the confining surface. The correlations show oscillatory decay in directions parallel to this surface too, with the decay length increasing significantly when the system boundary is approached. The framework of our theory allows for a systematic improvement of the accuracy of the results.

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“…He speculates about the possibility of the emergence of very long decay lengths caused by the effect of ion pairing. In another recent paper, Ciach [49] presented a density-functional linear response theory for an ionic liquid or concentrated ionic solution in a structureless solvent near a charged wall, which shows the emergence of decaying oscillatory profiles of the potential and chargedensity distributions, and the potentiality of an emergence of long decay ranges, which has not been yet explored.…”

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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Simple theory for oscillatory charge profile in ionic liquids near a charged wall

Cited by 22 publications

References 33 publications

The effect of short-range interaction and correlations on the charge and electric field distribution in a model solid electrolyte

The effect of short-range interaction and correlations on the charge and electric field distribution in a model solid electrolyte

Mesoscopic theory for systems with competing interactions near a confining wall

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

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