A nonlocal density functional theory of electric double layer: Symmetric electrolytes

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Abstract
The density functional theory of inhomogeneous classical neutral fluids is extended to study the structure of electric double layer using the restricted primitive model as well as the nonprimitive three‐component molecular solvent model. The formalism is based on a weighted density approach where the hard‐sphere contributions to the excess free energy density and the one‐particle correlation function are evaluated nonperturbatively using a position‐dependent effective density while the corresponding ionic part is obtained through a second‐order functional Taylor expansion around this effective density. The calculated results for the density profiles of the ions and the mean electrostatic potential are in good agreement with the available simulation results for the continuum solvent primitive model. The corresponding results for the nonprimitive molecular solvent model provide insight into the layering effect due to hard‐sphere exclusion and the charge inversion phenomena.