Structural and Dynamical Crossovers in Dense Electrolytes

Abstract

Electrostatic interactions fundamentally govern the structure and transport of electrolytes. In concentrated electrolytes, however, electrostatic and steric correlations, together with ion-solvent coupling, give rise to complex behavior, such as underscreening, that remains challenging to explain despite extensive theoretical effort. Using molecular dynamics simulations of primitive electrolytes with and without space-filling solvent particles, we elucidate the structural and dynamical crossovers and their connection that emerge with increasing salt concentration. Explicit-solvent electrolytes exhibit a screening transition from a charge-dominated dilute regime to a density-dominated concentrated regime, accompanied by dynamical crossovers in ion self-diffusion and ion-pair lifetimes. These dynamical crossovers display a marked discontinuity, unlike the smoother variation of the screening crossover, which originates from short-range ion-counterion structures. The pronounced growth of ionic clusters leads to a percolation transition only at higher concentrations, whereas the onset of the structural and dynamical crossovers is associated primarily with local ion pairing or small aggregates. Both structural and dynamical behaviors are found to depend sensitively on ion-solvent coupling: implicit-solvent electrolytes exhibit a screening transition between two charge-dominated regimes, accompanied by qualitatively distinct dynamical behavior. Finally, we demonstrate that the diffusion-corrected ion-pair lifetime provides a consistent descriptor linking ionic structure and dynamics across electrolyte systems.

14 pages, 6 figures for the main text, 41 pages, 33 figures for the supplemental material

References in corpus (21)

• The Electrostatic Screening Length in Concentrated Electrolytes Increases with Concentration
• Scaling analysis of the screening length in concentrated electrolytes
• Correlations from ion-pairing and the Nernst-Einstein equation
• Liquid friction on charged surfaces: from hydrodynamic slippage to electrokinetics
• Underscreening in concentrated electrolytes
• Kinetics of Ion Transport in Ionic Liquids: Two Dynamical Diffusion States
• Screening length for finite-size ions in concentrated electrolytes
• Theory of Ion Aggregation and Gelation in Super-Concentrated Electrolytes
• Primitive Model Electrolytes in the Near and Far Field: Decay Lengths from DFT and Simulations
• Charge Oscillations in Ionic Liquids: A Microscopic Cluster Model
• Screening Lengths in Ionic Fluids
• Anomalous Underscreening in the Restricted Primitive Model
• On the Gibbs-Thomson equation for the crystallization of confined fluids
• Conductance of concentrated electrolytes: multivalency and the Wien effect
• Ionic Associations and Hydration in the Electrical Double Layer of Water-in-Salt Electrolytes
• Overscreening and Underscreening in Solid-Electrolyte Grain Boundary Space-Charge Layers
• Stochastic density functional theory for ions in a polar solvent
• Donnan equilibrium in charged slit-pores from a hybrid nonequilibrium Molecular Dynamics / Monte Carlo method with ions and solvent exchange
• Cluster Formation induced by local dielectric saturation in Restricted Primitive Model Electrolytes
• Length scales in electrolytes
• Bridging Electrostatic Screening and Ion Transport in Lithium Salt-Doped Ionic Liquids