Structural properties of a planar electric double layer system formed by ions with symmetric off-centre charges: a Monte Carlo approach

The effect of off-centre charge ions on the structural properties of a planar electric double layer is explored by Monte Carlo simulations in the canonical ensemble. The ions are assumed to be equi-sized rigid spheres, with the charges located away from the geometrical centre of the spheres, but never outside the spheres. Both the positive and negative charges are located at the same distance from their respective parent sphere centres. The ionic species are immersed in a continuous structureless solvent in the vicinity of a uniformly charged and non-polarisable planar electrode. For a temperature of 298.15 K and molar concentration of 1 mol/dm3, the electrode-ion singlet distribution functions, the mean electrostatic potential and the orientation profile of the ions are reported for 1:1 ion valencies. The influence of the off-centre charge on the distribution functions seems to be more significant when the charge is closer to the surface of the spheres; on the other hand, the average orientation of the counterions tends to be linear near the charged electrode. No sign of charge inversion in the electrolyte was detected in this work.