Short-range solvent-solvent and ion-solvent correlations at metal-electrolyte interfaces: Parametrization and benchmarking

Short-range correlations in electrolyte solutions lead to oscillatory profiles of water polarization and ionic concentration at electrode-electrolyte interfaces. The recently developed density-potential-polarization functional theory (DPPFT) provides a comprehensive framework to incorporate these short-range correlation effects. In the present work, the parameters describing short-range solvent-solvent and ion-solvent correlations in DPPFT are determined from the wave- number-dependent dielectric susceptibility spectrum of pure water and ion solvation energies, respectively. The experimental trends in the ionic-radius-dependent hydration energies of alkali metal cations and halide anions are reproduced by the solvation model. Within this model, the charge hydration asymmetry is phenomenologically rationalized by a stronger short-range repulsion between cations and water molecules than between anions and water molecules. Using these parameters, DPPFT is then applied to describe short-range correlation effects at the Ag(111)-NaF aqueous electrolyte interface. The water polarization profiles obtained from DPPFT calculations agree with molecular dynamics simulations. Furthermore, as the strength of short-range ion-solvent repulsion increases, the peaks of anionic and cationic layers shift from regions near centers of positive and negative polarization charges, respectively, toward those of opposite sign, thereby preserving solvation configurations similar to those in bulk solution. This work develops a procedure for parametrizing short-range correlation effects within the DPPFT framework, thereby enabling a more quantitative and computationally efficient description of atomic-scale phenomena at electrochemical interfaces.