Dielectric decrement as a source of ion-specific effects

Abstract

Many theoretical studies were devoted in the past to ion-specific effects trying to interpret a large body of experimental evidence, such as surface tension at air/water interfaces and force measurements between charged objects. Although several mechanisms were suggested to explain the results, such as dispersion forces and specific surface-ion interactions, we would like to suggest another source of ion-specificity originating from the local variations of the dielectric constant due to the presence of ions in the solution. We present a mean-field model to account for the heterogeneity of the dielectric constant caused by the ions. In particular, for ions that decrease the dielectric constant we find a depletion of ions from the vicinity of charged surfaces. For a two-plate system, the same effect leads to an increase of the pressure in between two surfaces. Our results suggest that the effect of ions on the local dielectric constant should be taken into account when interpreting experiments that address ion-specific effects.

Finite field methods for the supercell modeling of charged insulator/electrolyte interfaces

“…There are several effects which in a realistic model could lead to non-linearity, such as dielectric saturation and coupling to stress [26,27]. In fact, the reason for the so called dielectric decrement at charged interfaces is still under debate [81]. Also, in DFTMD simulation the solid is free to move and reorganization of the atomic structure of the insulator could also play a role.…”

Energies and pressures in viruses: contribution of nonspecific electrostatic interactions

“…We shall emphasize the non-specific aspects of the contributions electrostatic interactions and will thus avoid a detailed exposition of the ion-specific effects 46,47 . This means that we do not deal with chemical specificity of different ions that may drastically modify electrostatic interactions.…”

Hofmeister effects in micromolar electrolyte solutions

“…4,[23][24][25][26][27] The full consequences of quantum fluctuations within extended dielectric media in the presence of charges are being investigated using molecular dynamics simulations, 28 and continuum non-local electrostatics models based on a dielectric function ε(r, r ) of both the local electric field and the long-range polarization of the surrounding medium. [29][30][31] A key parameter in models dealing with cooperative effects is the length of correlations, λ, in this case those induced a) Authors to whom correspondence should be addressed. Electronic addresses: enami.shinichi.3r@kyoto-u.ac.jp and ajcoluss@caltech.edu.…”