Electrolytes and the Electric Double Layer

Attard, Phil

doi:10.1002/9780470141519.ch1

Cited by 125 publications

(81 citation statements)

References 356 publications

(21 reference statements)

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“…28 Despite its near-ubiquitous use, the GC-LDA (and eq 17 more generally) has long been known to fail for various reasons. Boltzmann-distributed densities grow exponentially with ϕ̃and can yield volume fractions exceeding close packing of finite-sized ions at reasonable potentials.…”

Section: Electric Double-layer Modelsmentioning

confidence: 99%

Electric Double-Layer Structure in Primitive Model Electrolytes: Comparing Molecular Dynamics with Local-Density Approximations

et al. 2015

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ABSTRACT:We evaluate the accuracy of local-density approximations (LDAs) using explicit molecular dynamics simulations of binary electrolytes comprised of equisized ions in an implicit solvent. The Bikerman LDA, which considers ions to occupy a lattice, poorly captures excluded volume interactions between primitive model ions. Instead, LDAs based on the Carnahan− Starling (CS) hard-sphere equation of state capture simulated values of ideal and excess chemical potential profiles extremely well, as well as the relationship between surface charge density and electrostatic potential. Excellent agreement between the EDL capacitances predicted by CS-LDAs and computed in molecular simulations is found even in systems where ion correlations drive strong density and free charge oscillations within the EDL, despite the inability of LDAs to capture the oscillations in the detailed EDL profiles.

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Section: Electric Double-layer Modelsmentioning

confidence: 99%

Electric Double-Layer Structure in Primitive Model Electrolytes: Comparing Molecular Dynamics with Local-Density Approximations

et al. 2015

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“…The density of monovalent ions displays a clear depletion near the walls, despite the absence of any external fields in the region between the walls, whereas a pure mean-field theory predicts a constant density. In hightemperature expansions or saddle point approximations (26,35,36), this effect appears only in the higher-order corrections and is purely of a correlational origin. Fig.…”

Section: Deformation Of the Screening Layer-neutral Boundariesmentioning

confidence: 99%

Tunable soft structure in charged fluids confined by dielectric interfaces

Zwanikken¹,

Cruz

2013

Proc. Natl. Acad. Sci. U.S.A.

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Fluids of charged particles act as the supporting medium for chemical reactions and physical, dynamical, and biological processes. The local structure in an electrolytic background is deformed by micro-and nanoscopic polarizable objects. Vice versa, the forces between the objects are regulated by the cohesive properties of the background. We study here the range and strength of these forces and the microscopic origin from which they emerge. We find the forces to be sensitively dependent on the material properties of the charged fluid and the immersed solutes. The induced interactions can be varied over decades, offering high tunability and aided by accurate theory, control in experiments and applications. To distinguish correlational effects from simple ionic screening, we describe electrolyte-induced forces between neutral objects. The interplay of thermal motion, short-range repulsions, and electrostatic forces is responsible for a soft structure in the fluid. This structure changes near polarizable interfaces and causes diverse attractions between confining walls that seem well-exploited by microbiological systems. For parameters that correspond to monovalent electrolytes in biologically and technologically relevant aqueous environments, we find induced forces between nanoscopic areas of the order of piconewtons over a few nanometers. T he region where different phases meet at an interface hosts the regulatory processes that determine the face of the Earth from a global scale down to the microscopic-length scales. These processes include the chemical reactions in the atmosphere and the Earth's crust at the water-air and water-solid interfaces (1) as well as the highly specific processes in biology that are coordinated by membranes and complex macromolecular agents (2). Interfaces can localize reactive components, mediate interactions, and allow components in different phases to meet in a selective way, offering tunable reaction rates over a vast range of magnitudes. The catalytic qualities of interfaces are broadly exploited in industrial processing that involves an ample variety of applications, such as metal extraction, water purification, phase transfer catalysis, and reprocessing of nuclear waste. In addition to the chemical aspects, interfaces also have distinct physical properties, which find their applications in transistors and supercapacitors as well as emulsion stabilization.In this paper, we highlight the physical properties of the liquidsolid interface, with a strong focus on fluids of charged particles that are confined by two dielectric boundaries. In the theoretical analysis, the charged particles are characterized by the charge q ± and the maximum coupling strength set by an effective hardsphere radius a ± and the Coulomb potential at contact. The solvent is considered implicitly by a constant permittivity « s relative to the vacuum permittivity. By adopting these simplifications that constitute the so-called Primitive Model, we can connect to a tradition of research and expand on familiar kno...

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“…Such a configuration of plates (FF) can only be possible after a significant reduction in the strong electrical charge on plate faces, which was not the case herein, particularly in NaCl solution. The ion-ion correlation effect makes the FF interaction much weaker when bivalent cations are present in a solution, and it even becomes attractive, as justified by numerous Monte-Carlo simulations and studies of density functional theory (or integral equation approaches such as the hyper-netted chain method) on a primitive model of electrical double layers [41]. The flocculation of clay suspensions has been referred to as a consequence of EF and EE associations, responsible for the continuous gel-like structure in montmorillonite clay suspensions [42].…”

Section: Discussionmentioning

confidence: 99%