The European Physical Journal Special Topics

, Volume 226, Issue 4, pp 725–736 | Cite as

Simulation of weak polyelectrolytes: a comparison between the constant pH and the reaction ensemble method

  • Jonas LandsgesellEmail author
  • Christian Holm
  • Jens SmiatekEmail author
Regular Article
Part of the following topical collections:
  1. Recent Advances in Phase Transitions and Critical Phenomena


The reaction ensemble and the constant pH method are well-known chemical equilibrium approaches to simulate protonation and deprotonation reactions in classical molecular dynamics and Monte Carlo simulations. In this article, we demonstrate the similarity between both methods under certain conditions. We perform molecular dynamics simulations of a weak polyelectrolyte in order to compare the titration curves obtained by both approaches. Our findings reveal a good agreement between the methods when the reaction ensemble is used to sweep the reaction constant. Pronounced differences between the reaction ensemble and the constant pH method can be observed for stronger acids and bases in terms of adaptive pH values. These deviations are due to the presence of explicit protons in the reaction ensemble method which induce a screening of electrostatic interactions between the charged titrable groups of the polyelectrolyte. The outcomes of our simulation hint to a better applicability of the reaction ensemble method for systems in confined geometries and titrable groups in polyelectrolytes with different pK a values.


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Copyright information

© EDP Sciences and Springer 2017

Authors and Affiliations

  1. 1.Institute for Computational Physics, University of StuttgartStuttgartGermany

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