Primitive Model Electrolytes in the Near and Far Field: Decay Lengths from DFT and Simulations

Abstract

Inspired by recent experimental observations of anomalously large decay lengths in concentrated electrolytes, we revisit the Restricted Primitive Model (RPM) for an aqueous electrolyte. We investigate the asymptotic decay lengths of the one-body ionic density profiles for the RPM in contact with a planar electrode using classical Density Functional Theory (DFT), and compare these with the decay lengths of the corresponding two-body correlation functions in bulk systems, obtained in previous Integral Equation Theory (IET) studies. Extensive Molecular Dynamics (MD) simulations are employed to complement the DFT and IET predictions. Our DFT calculations incorporate electrostatic interactions between the ions using three different (existing) approaches: one based on the simplest mean field treatment of Coulomb interactions (MFC), whilst the other two employ the Mean Spherical approximation (MSA). The MSAc invokes only the MSA bulk direct correlation function whereas the MSAu also incorporates the MSA bulk internal energy. Although MSAu yields profiles that agree best with MD simulations in the near field, in the far field we observe that the decay lengths are consistent between IET, MSAc, and MD simulations, whereas those from MFC and MSAu deviate significantly. Using DFT we calculated the solvation force, which relates directly to surface force experiments. We find that its decay length is neither qualitatively nor quantitatively close to the large decay lengths measured in experiments and conclude that the latter cannot be accounted for by the primitive model. The anomalously large decay lengths found in surface force measurements require an explanation that lies beyond primitive models.

References in corpus (6)

• The Electrostatic Screening Length in Concentrated Electrolytes Increases with Concentration
• Scaling analysis of the screening length in concentrated electrolytes
• Underscreening in concentrated electrolytes
• Solvation force for long ranged wall-fluid potentials
• On the decay of the pair correlation function and the line of vanishing excess isothermal compressibility in simple fluids
• Comments on the linear modified Poisson-Boltzmann equation in electrolyte solution theory

Cited by in corpus (39)

• Neural functional theory for inhomogeneous fluids: Fundamentals and applications
• Anomalous Underscreening in the Restricted Primitive Model
• Perspective: How to overcome dynamical density functional theory
• Force density functional theory in- and out-of-equilibrium
• The Differential Capacitance as a probe for the electric double layer structure and the electrolyte bulk composition
• Noether-Constrained Correlations in Equilibrium Liquids
• Learning classical density functionals for ionic fluids
• Why neural functionals suit statistical mechanics
• Hyper-density functional theory of soft matter
• Learning Neural Free-Energy Functionals with Pair-Correlation Matching
• The Primitive Model in Classical Density Functional Theory: Beyond the Standard Mean-Field Approximation
• Overscreening and Underscreening in Solid-Electrolyte Grain Boundary Space-Charge Layers
• Electric-field-induced oscillations in ionic fluids: a unified formulation of modified Poisson-Nernst-Planck models and its relevance to correlation function analysis
• Noether invariance theory for the equilibrium force structure of soft matter
• Adsorption of polyelectrolytes in the presence of varying dielectric discontinuity between solution and substrate
• Extension of the primitive model by hydration shells and its impact on the reversible heat production during the buildup of the electric double layer
• Cluster Formation induced by local dielectric saturation in Restricted Primitive Model Electrolytes
• Systematic incorporation of the ionic hard-core size into the Debye-Huckel theory via the cumulant expansion of the Schwinger-Dyson equations
• In-plane structure of the electric double layer in the primitive model using classical density functional theory
• Dynamic Decay and Superadiabatic Forces in the van Hove Dynamics of Bulk Hard Sphere Fluids
• Stochastic Density Functional Theory on Lane Formation in Electric-Field-Driven Ionic Mixtures: Flow-Kernel-Based Formulation
• Solvent-induced ion clusters generate long-ranged double-layer forces at high ionic strengths
• Gauge invariance and hyperforce correlation theory for equilibrium fluid mixtures
• Exceptionally strong double-layer barriers generated by polyampholyte salt
• Interactions between polyelectrolytes mediated by ordering and orientation of multivalent non-spherical ions in salt solutions
• Bridging Electrostatic Screening and Ion Transport in Lithium Salt-Doped Ionic Liquids
• Self-consistent electrostatic formalism of bulk electrolytes based on the asymmetric treatment of the short- and long-range ion interactions
• Electric field-induced clustering in nanocomposite films of highly polarizable inclusions
• Mutual effect of charge- and number-density correlations in ionic liquids and concentrated electrolytes
• Structural and Dynamical Crossovers in Dense Electrolytes
• Brownian dynamics simulations of electric double-layer capacitors with tunable metallicity
• Unified microscopic theory of equilibrium thermodynamics and ion association in aqueous and non-aqueous electrolytes with explicit hard-core size
• Pole Analysis of the Inter-Replica Correlation Function in a Two-Replica System as a Binary Mixture: Mean Overlap in the Cluster Glass Phase
• Polar Liquids at Charged Interfaces: A Dipolar Shell Theory
• Underscreening and hidden ion structures in large scale simulations of concentrated electrolytes
• On the electrical double layer capacitance of the restricted primitive model: a link between the mesoscopic theory and the associative mean spherical approximation
• Absence of anomalous underscreening in highly concentrated aqueous electrolytes confined between smooth silica surfaces
• On the statistical theory of strong electrolytes and high-temperature plasmas: new applications of the work of Yukhnovskii and Kelbg
• Polyampholyte model of ion clusters: double-layer interactions in the presence of dissociated simple salt