Application of the singlet reference interaction site model to the primitive model double layer

Abstract

The Singlet Reference Interaction Site Model (SRISM) is employed to a structural study of the planar electric double layer using the primitive model of the double layer in which the solvent is implicit, being characterized by a dielectric constant, the ions are represented by charged hard spheres, while the electrode is a uniformly charged flat surface. The primitive model double layer has the advantage that simulation results encompassing a wide range of physical states are available for comparison purposes. The predicted results are compared with some recent simulations and an earlier simulation for an extreme case. The SRISM with closures based on the hypernetted chain show the most promise of the closures considered here. Although the SRISM results are not perfect, the accuracy of SRISM with the best closures is often comparable to the modified Poisson–Boltzmann theory, while the density functional theory seems more accurate for the extreme cases. The SRSIM has the advantage that explict water molecules can be included and solutions can be obtained for high densities. Furthermore, since molecular ions can be treated, SRISM seems suitable for the study of ionic liquids.

Keywords:

• electrical double layer
• integral equations
• reference interaction site model
• electrolytes
• hypernetted chain approximation