Structure of a planar electric double layer formed by fused dimer cations and fused dimer anions: a Monte Carlo simulation study

The structure of a planar double layer system containing both positively charged and negatively charged dimer ions is explored using Monte Carlo simulation in the canonical ensemble. The dimer ions are immersed in a structureless solvent mimicked by a dielectric continuum adjacent to a charged electrode. The dimer cations and dimer anions consist of two equally sized hard spheres fused together; in each dimer, one sphere is charged, while the other is neutral. For a bulk concentration of 1 mol/dm3 and symmetric dimer valencies of 1:1, singlet distribution functions and the average orientation of the dimers perpendicular to the electrode are obtained for both positive and negative electrode surface charges. At the same fusion levels for both species of dimers, more structure is observed when the fusion level is low rather than when this level is high. Additionally, the coion and counterion profiles tend to be inverted when the electrode surface charge is reversed.