Polarization Deficiency and Excess Free Energy of Ion Hydration in Electric Fields

Gavryushov, Sergei; Linse, Per

doi:10.1021/jp030035w

Cited by 24 publications

(78 citation statements)

References 71 publications

(108 reference statements)

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“…The external electrostatic field along the x or y direction ( E X ext , E Y ext ) was applied to a pure water cluster, and the relation between the dipole moment of TIP3P water and the net electrostatic field at the oxygen atom of TIP3P water was consistent with the results obtained in previous works [37,38]. The external electrostatic field along the x or y direction ( E X ext , E Y ext ) was applied to a water cluster containing one or two charged atoms, and the dependences of the mean force and the potential of mean force (PMF) between the charged solutes on E ext were studied using MD simulations [40]. The differences between the mean force estimated from a continuum solvent and that computed using MD simulations were discussed.…”

Section: Introductionsupporting

confidence: 77%

Dependence of Interaction Free Energy between Solutes on an External Electrostatic Field

Yang

2013

IJMS

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To explore the athermal effect of an external electrostatic field on the stabilities of protein conformations and the binding affinities of protein-protein/ligand interactions, the dependences of the polar and hydrophobic interactions on the external electrostatic field, −Eext, were studied using molecular dynamics (MD) simulations. By decomposing Eext into, along, and perpendicular to the direction formed by the two solutes, the effect of Eext on the interactions between these two solutes can be estimated based on the effects from these two components. Eext was applied along the direction of the electric dipole formed by two solutes with opposite charges. The attractive interaction free energy between these two solutes decreased for solutes treated as point charges. In contrast, the attractive interaction free energy between these two solutes increased, as observed by MD simulations, for Eext = 40 or 60 MV/cm. Eext was applied perpendicular to the direction of the electric dipole formed by these two solutes. The attractive interaction free energy was increased for Eext = 100 MV/cm as a result of dielectric saturation. The force on the solutes along the direction of Eext computed from MD simulations was greater than that estimated from a continuum solvent in which the solutes were treated as point charges. To explore the hydrophobic interactions, Eext was applied to a water cluster containing two neutral solutes. The repulsive force between these solutes was decreased/increased for Eext along/perpendicular to the direction of the electric dipole formed by these two solutes.

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Section: Introductionsupporting

confidence: 77%

Dependence of Interaction Free Energy between Solutes on an External Electrostatic Field

Yang

2013

IJMS

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“…2012). In (1.2), we assume that the dielectric permittivity of water ε w is equal to its bulk value, which is valid for electric fields below 0.1 V/nm (Booth 1951; Danielewicz-Ferchmin & Ferchmin 2002; Gavryushov & Linse 2003; Joshi et al 2004). α > 0 corresponds to the dielectric decrement.…”

Section: Introductionmentioning

confidence: 99%

The influence of dielectric decrement on electrokinetics

Zhao

Zhai

2013

J. Fluid Mech.

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We treat the dielectric decrement induced by excess ion polarization as a source of ion specificity and explore its impact on electrokinetics. We employ a modified Poisson-Nernst-Planck (PNP) equations accounting for the dielectric decrement. The dielectric decrement is determined by the excess ion polarization parameter α and when α = 0 the standard PNP model is recovered. Our model shows that ions saturate at large zeta potentials (ζ). Because of ion saturation, a condensed counterion layer forms adjacent to the charged surface, introducing a new length scale, the thickness of the condensed layer (lc). For the electro-osmotic mobility, the dielectric decrement weakens the electro-osmotic flow owing to the decrease of the dielectric permittivity. At large ζ, when α ≠ 0, the electro-osmotic mobility is found to be proportional to ζ/2, in contrast to ζ predicted by the standard PNP model. This is attributed to ion saturation at large ζ. In terms of the electrophoretic mobility Me, we carry out both an asymptotic analysis in the thin-double-layer limit and solve the full modified PNP model to compute Me. Our analysis reveals that the impact of the dielectric decrement is intriguing. At small and moderate ζ, the dielectric decrement decreases Me with an increasing α. At large ζ, it is well known that the surface conduction becomes significant and plays an important role in determining Me. It is observed that the dielectric decrement effectively reduces the surface conduction. Hence in stark contrast, Me increases as α increases. Our predictions of the contrast dependence of the mobility on α at different zeta potentials qualitatively agree with experimental results on the dependence of the mobility among ions and provide a possible explanation for such ion specificity. Finally, the comparisons between the thin-double-layer asymptotic analysis and the full simulations of the modified PNP model suggest that at large ζ the validity of the thin-double-layer approximation is determined by lc rather than the traditional Debye length.

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“…For |φ ′ | 0.25 V nm −1 , to a good approximation, the magnitude of the induced dipole can be considered proportional to the electric field [24]; therefore, we assume this to be the case and that the induced dipole is aligned parallel (or anti-parallel) to the electric field…”

Section: Excess Ion Polarizabilitymentioning

confidence: 99%

“…In addition to modifying the permittivity of the solution, the excess polarizability also causes the electrochemical potential of the ions to grow quadratically with the electric field [24] for |φ ′ | < 0.25 V nm −1 ; for larger fields, dielectric saturation of the solvent causes the variation to become linear [11]. This growth in the species energy, due to the induced dipole on the ions in the high field region of the EDL, counterbalances the increased Coulombic force experienced by the counter-charge at high potentials, leading to dielectrophoretic saturation.…”

Section: Introductionmentioning

confidence: 99%

The influence of excluded volume and excess ion polarisability on the capacitance of the electric double layer

Minton

Lue

2016

Molecular Physics

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This version is available at https://strathprints.strath.ac.uk/55894/ Strathprints is designed to allow users to access the research output of the University of Strathclyde. Unless otherwise explicitly stated on the manuscript, Copyright © and Moral Rights for the papers on this site are retained by the individual authors and/or other copyright owners. Please check the manuscript for details of any other licences that may have been applied. You may not engage in further distribution of the material for any profitmaking activities or any commercial gain. You may freely distribute both the url (https://strathprints.strath.ac.uk/) and the content of this paper for research or private study, educational, or not-for-profit purposes without prior permission or charge.Any correspondence concerning this service should be sent to the Strathprints administrator: strathprints@strath.ac.ukThe Strathprints institutional repository (https://strathprints.strath.ac.uk) is a digital archive of University of Strathclyde research outputs. It has been developed to disseminate open access research outputs, expose data about those outputs, and enable the management and persistent access to Strathclyde's intellectual output. We apply a modified Poisson-Boltzmann theory which permits ions of different sizes and excess polarizabilities to the study of these properties' effects on the differential capacitance of the electric double layer. For a planar electrode, we find an analytical expression for the differential capacitance, which is examined in the limits of low and high applied potential. In the low potential limit, a reduction of the solution relative permittivity caused by the ion polarizability causes the differential capacitance to decrease above a certain concentration, relative to the Gouy-Chapman-Stern theory. A similar effect is observed for the excluded volume, but only if the ions are of different sizes. In the high potential limit, the differential capacitance decreases inversely with the square root of the applied voltage. In a mixed electrolyte, asymmetries in both ion size and excess polarizability alter the surface adsorption of species: at high potentials, smaller ions displace larger ions and less polarizable ions displace more polarizable ions. The extent of the displacement agrees favorably with experimental data. A further consequence of this displacement is the appearance of a second peak in the differential capacitance, which is enhanced by excess ion polarizability.

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Polarization Deficiency and Excess Free Energy of Ion Hydration in Electric Fields

Cited by 24 publications

References 71 publications

Dependence of Interaction Free Energy between Solutes on an External Electrostatic Field

Dependence of Interaction Free Energy between Solutes on an External Electrostatic Field

The influence of dielectric decrement on electrokinetics

The influence of excluded volume and excess ion polarisability on the capacitance of the electric double layer

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