Figure 2.

Superionic state in slit nanopores. (a) Model of a slit-shaped metallic pore. The slit width L is comparable to the ion diameter a = a_±. A potential difference u is applied to the pore walls with respect to bulk electrolyte (not shown). (b) Absolute value of the electrostatic interaction energy between two ions in a nonconducting and metallic slit. The circles exemplify the locations of the ions. The interactions energy is shown only in the regions allowed by steric exclusion. Ion diameter 2a = 0.5 nm and the pore width L = 0.6 nm. (c) Absolute value of the Coulomb interaction energy and the interionic interactions in the superionic state for two slit widths. The ions reside on the symmetry plane of the slit, and r is the distance between them. The interaction energy is given by eq 9. The shaded area shows the region of steric exclusion. (d) Effective image-charge ion-pore wall attraction given by eq 12, shown for two indicated pore widths The thin vertical lines show the locations of the center of an ion that are closest to the pore walls. Note that the are four vertical lines, two for each slit width; the pore walls are at z = 0 and z/L = 1. In all plots, the in-pore relative permittivity ε = 2.5 and temperature T = 293 K.