Charge-Induced Fluctuation Forces in Graphitic Nanostructures

Drosdoff, D.; Bondarev, I. V.; Widom, A.; Podgornik, Rudolf; Woods, Lilia M.

doi:10.1103/physrevx.6.011004

Cited by 14 publications

(24 citation statements)

References 41 publications

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“…It would be interesting to extend the present work to open systems, in which the exchange of electrolyte with a reservoir results in fluctuations in the number of ions and solvent molecules, which play an important role in the context of blue energy harvesting [57]. Other directions include the simulation of reactive systems [58] for electrochemical applications, as well as the coupling of electrical and mechanical properties, including forces induced by charge fluctuations [59] or to analyze recent Surface Force Balance experiments [60].…”

Section: Discussionmentioning

confidence: 99%

Charge fluctuations from molecular simulations in the constant-potential ensemble

Scalfi

Limmer

Coretti

et al. 2020

Phys. Chem. Chem. Phys.

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We revisit the statistical mechanics of charge fluctuations in capacitors. In constant-potential classical molecular simulations, the atomic charge of electrode atoms are treated as additional degrees of freedom which evolve in time so as to satisfy the constraint of fixed electrostatic potential for each configuration of the electrolyte. The present work clarifies the role of the overall electroneutrality constraint, as well as the link between the averages computed within the Born-Oppenheimer approximation and that of the full constant-potential ensemble. This allows us in particular to derive a complete fluctuation-dissipation relation for the differential capacitance, that includes a contribution from the charge fluctuations (around the charges satisfying the constant-potential and electroneutrality constraints) also present in the absence of an electrolyte. We provide a simple expression for this contribution from the elements of the inverse of the matrix defining the quadratic form of the fluctuating charges in the energy. We then illustrate numerically the validity of our results, and recover the expected result for an empty capacitor with structureless electrodes at large inter-electrode distances. By considering a variety of liquids between graphite electrodes, we confirm that this contribution to the total differential capacitance is small compared to that induced by the thermal fluctuations of the electrolyte.

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Section: Discussionmentioning

confidence: 99%

Charge fluctuations from molecular simulations in the constant-potential ensemble

Scalfi

Limmer

Coretti

et al. 2020

Phys. Chem. Chem. Phys.

View full text Add to dashboard Cite

show abstract

“…Work along these lines is in progress. As a final remark, we note that the electrolyte fluctuation induced force discussed here has to be considered even in the absence of a mean-field interaction arising from surface charges, and that other forces induced by surface-charge fluctuations may also have to be taken into account under confinement by conducting walls in or out of equilibrium [30,31].…”

Section: Discussionmentioning

confidence: 99%

Casimir force in dense confined electrolytes

et al. 2018

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Understanding the force between charged surfaces immersed in an electrolyte solution is a classic problem in soft matter and liquid-state theory. Recent experiments showed that the force decays exponentially but the characteristic decay length in a concentrated electrolyte is significantly larger than what liquid-state theories predict based on analysing correlation functions in the bulk electrolyte. Inspired by the classical Casimir effect, we consider an alternative mechanism for force generation, namely the confinement of density fluctuations in the electrolyte by the walls.We show analytically within the random phase approximation, which assumes the ions to be point charges, that this fluctuation-induced force is attractive and also decays exponentially, albeit with a decay length that is half of the bulk correlation length. These predictions change dramatically when excluded volume effects are accounted for within the mean spherical approximation. At high ion concentrations the Casimir force is found to be exponentially damped oscillatory as a function of the distance between the confining surfaces. Our analysis does not resolve the riddle of the anomalously long screening length observed in experiments, but suggests that the Casimir force due to mode restriction in density fluctuations could be an hitherto under-appreciated source of surface-surface interaction.

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“…Charge induced fluctuation forces in graphitic nanostructures, similar to those considered here, have been described in Ref. [8]: in that case, instead of the presence of a charge reservoir, charge fluctuations are allowed by connecting the conductors among them (the particular case considered there is that of a parallel plate capacitor with the plates connected by a wire). The charge density correlation is evaluated using the fluctuation-dissipation theorem.…”

Section: Discussionmentioning

confidence: 83%

Difference between the vacuum Casimir energies for grounded and isolated conductors

2016

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We study the vacuum (i.e., zero-temperature) Casimir energy for a system of neutral conductors which are isolated , as opposed to grounded. The former is meant to describe a situation where the total charge on each conductor, as well as all of its fluctuations, vanishes, while the latter describes a situation where the conductors are connected to a charge reservoir. We compute the difference between the vacuum energies for a given system of conductors, but subjected to the two different conditions stated above. The results can be written in terms of a generalized, frequency-dependent capacitance matrix of the system. Using a multipolar expansion, we show that the grounded Casimir energy includes a monopole-monopole interaction term that is absent in the isolated case in the large distance limit.

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Charge-Induced Fluctuation Forces in Graphitic Nanostructures

Cited by 14 publications

References 41 publications

Charge fluctuations from molecular simulations in the constant-potential ensemble

Charge fluctuations from molecular simulations in the constant-potential ensemble

Casimir force in dense confined electrolytes

Difference between the vacuum Casimir energies for grounded and isolated conductors

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