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The transition from a molecular to a continuum solvent in electrical double layers showing ion-ion correlation effects.

Pegado, Luis LU ; Jönsson, Bo LU and Wennerström, Håkan LU (2011) In Physical chemistry chemical physics : PCCP 13. p.16324-16335
Abstract
We analyze, using Monte Carlo simulations, how a dielectric medium, modeled as a Stockmayer fluid, modulates the force between two similarly charged surfaces. A major objective is to provide a basis for understanding the strengths and weaknesses of the primitive model. The system studied has uniformly charged walls separated by counterions and solvent, where the latter is kept at constant chemical potential as the separation between the walls is varied. For two different types of Stockmayer fluids, one with a "low" (e ~ 4.4) and one with a "high" (e ~20) relative dielectric permittivity, the size of the solvent molecules is varied systematically. As the size of the solvent molecules becomes smaller one approaches the continuum limit, where... (More)
We analyze, using Monte Carlo simulations, how a dielectric medium, modeled as a Stockmayer fluid, modulates the force between two similarly charged surfaces. A major objective is to provide a basis for understanding the strengths and weaknesses of the primitive model. The system studied has uniformly charged walls separated by counterions and solvent, where the latter is kept at constant chemical potential as the separation between the walls is varied. For two different types of Stockmayer fluids, one with a "low" (e ~ 4.4) and one with a "high" (e ~20) relative dielectric permittivity, the size of the solvent molecules is varied systematically. As the size of the solvent molecules becomes smaller one approaches the continuum limit, where the primitive model should give an increasingly more accurate representation. We find that having an explicit description of the solvent gives rise to an oscillatory component in the force between the surfaces. The wavelength of the oscillations reflects the diameter of the solvent molecules. The smaller the solvent molecules the smaller are the amplitudes of the oscillations. On integrating the force curves to yield interaction free energies the oscillatory features become less apparent. For the smallest solvent size studied the interaction curves show clear similarities with those obtained from the primitive model. The qualitative effect of the dielectric screening is recovered. It is found that the deviations from the mean field description also appear for the molecular solvent. All this suggests that there are no major deviations due to the neglect of many-body contributions in the solvent-averaged potential of the primitive model. This also holds for the incompressibility assumption implicitly applied when using the primitive model. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Physical chemistry chemical physics : PCCP
volume
13
pages
16324 - 16335
publisher
Royal Society of Chemistry
external identifiers
  • wos:000294441900026
  • pmid:21845284
  • scopus:80053293438
ISSN
1463-9084
DOI
10.1039/c1cp20514e
language
English
LU publication?
yes
id
c6231705-d5bb-4616-9f7f-05c01a755c98 (old id 2151021)
date added to LUP
2011-08-31 10:36:48
date last changed
2017-09-24 03:58:02
@article{c6231705-d5bb-4616-9f7f-05c01a755c98,
  abstract     = {We analyze, using Monte Carlo simulations, how a dielectric medium, modeled as a Stockmayer fluid, modulates the force between two similarly charged surfaces. A major objective is to provide a basis for understanding the strengths and weaknesses of the primitive model. The system studied has uniformly charged walls separated by counterions and solvent, where the latter is kept at constant chemical potential as the separation between the walls is varied. For two different types of Stockmayer fluids, one with a "low" (e ~ 4.4) and one with a "high" (e ~20) relative dielectric permittivity, the size of the solvent molecules is varied systematically. As the size of the solvent molecules becomes smaller one approaches the continuum limit, where the primitive model should give an increasingly more accurate representation. We find that having an explicit description of the solvent gives rise to an oscillatory component in the force between the surfaces. The wavelength of the oscillations reflects the diameter of the solvent molecules. The smaller the solvent molecules the smaller are the amplitudes of the oscillations. On integrating the force curves to yield interaction free energies the oscillatory features become less apparent. For the smallest solvent size studied the interaction curves show clear similarities with those obtained from the primitive model. The qualitative effect of the dielectric screening is recovered. It is found that the deviations from the mean field description also appear for the molecular solvent. All this suggests that there are no major deviations due to the neglect of many-body contributions in the solvent-averaged potential of the primitive model. This also holds for the incompressibility assumption implicitly applied when using the primitive model.},
  author       = {Pegado, Luis and Jönsson, Bo and Wennerström, Håkan},
  issn         = {1463-9084},
  language     = {eng},
  pages        = {16324--16335},
  publisher    = {Royal Society of Chemistry},
  series       = {Physical chemistry chemical physics : PCCP},
  title        = {The transition from a molecular to a continuum solvent in electrical double layers showing ion-ion correlation effects.},
  url          = {http://dx.doi.org/10.1039/c1cp20514e},
  volume       = {13},
  year         = {2011},
}