A cell-model study on counterion fluctuations in macroionic systems: Effect of non-extensiveness in entropy

Yiing-Rei Chen, Chi Lun Lee

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Abstract

Rigorously speaking, entropy is slightly non-extensive, and this non-extensiveness, which characterizes the degree of fluctuations, can contribute to effective interactions between mesoscopic objects. In this paper, we consider a pair of macroions, each accompanied by 1000 counterions, and with a cell-model description we demonstrate that the slow variation of non-extensiveness in counterion entropy over macroionic distance leads to an effective long-range attraction between the macroions. With the aid of Monte Carlo simulation and a Bragg-Williams theory including counterion number fluctuations, we find the depth of attraction in free energy to be approximately 0.2kBT. The observation in our cell-model study provides an insight for further understanding of effective interactions in real macroionic systems.

Original languageEnglish
Pages (from-to)297-303
Number of pages7
JournalPhysical Chemistry Chemical Physics
Volume16
Issue number1
DOIs
Publication statusPublished - 2014 Jan 7

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ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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