On the contact values of the density profiles in an electric double layer using density functional theory

TL;DR

This paper evaluates the accuracy of density functional theory in predicting contact values of ion distributions in an electric double layer, using a recently proposed contact value theorem and Monte Carlo data for validation.

Contribution

It applies a new local second contact value theorem to assess the contact behavior of electrode-ion distributions predicted by density functional theory, comparing with simulation data.

Findings

Theoretical contact values agree semi-quantitatively with simulations.

Product of co- and counterion contact values shows qualitative agreement with deviations at higher concentrations.

The approach provides a reasonable assessment of density functional theory predictions for electric double layers.

Abstract

A recently proposed local second contact value theorem [Henderson D., Boda D., J. Electroanal. Chem., 2005, 582, 16] for the charge profile of an electric double layer is used in conjunction with the existing Monte Carlo data from the literature to assess the contact behavior of the electrode-ion distributions predicted by the density functional theory. The results for the contact values of the co- and counterion distributions and their product are obtained for the symmetric valency, restricted primitive model planar double layer for a range of electrolyte concentrations and temperatures. Overall, the theoretical results satisfy the second contact value theorem reasonably well, the agreement with the simulations being semi-quantitative or better. The product of the co- and counterion contact values as a function of the electrode surface charge density is qualitative with the simulations with increasing deviations at higher concentrations.