Condensed Matter Physics, 2017, vol. 20, No. 3, 33801

Title: Charge reversal and surface charge amplification in asymmetric valence restricted primitive model planar electric double layers in the modified Poisson-Boltzmann theory
  L.B. Bhuiyan (Laboratory of Theoretical Physics, Department of Physics, Box 70377, University of Puerto Rico, San Juan, Puerto Rico 00936-8377, USA) ,
  C.W. Outhwaite (Department of Applied Mathematics, University of Sheffield, Sheffield S3 7RH, UK)

The modified Poisson-Boltzmann theory of the restricted primitive model double layer is revisited and recast in a fresh, slightly broader perspective. Derivation of relevant equations follow the techniques utilized in the earlier MPB4 and MPB5 formulations and clarifies the relationship between these. The MPB4, MPB5, and a new formulation of the theory are employed in an analysis of the structure and charge reversal phenomenon in asymmetric 2:1/1:2 valence electrolytes. Furthermore, polarization induced surface charge amplification is studied in 3:1/1:3 systems. The results are compared to the corresponding Monte Carlo simulations. The theories are seen to predict the "exact" simulation data to varying degrees of accuracy ranging from qualitative to almost quantitative. The results from a new version of the theory are found to be of comparable accuracy as the MPB5 results in many situations. However, in some cases involving low electrolyte concentrations, theoretical artifacts in the form of un-physical "shoulders" in the singlet ionic distribution functions are observed.

Key words: electric double layer, imaging, restricted primitive model, modified Poisson-Boltzmann theory, Monte Carlo simulations
PACS: 82.45.Fk, 61.20.Qg, 82.45.Gj

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