Structural and dynamical properties of concentrated alkali- and alkaline-earth metal chloride aqueous solutions.

This article focuses on the structural and dynamic properties of concentrated aqueous electrolytes containing LiCl, NaCl, KCl, MgCl₂, and CaCl₂, investigated through classical molecular dynamics (MD) simulations. The study reveals that cation-chloride contact ion pairs (CIP) are prominent in NaCl, KCl, and CaCl₂ solutions, while water-bridged ion pairs are abundant across all solutions; cation-bridged chloride–chloride pairs appear distinctly only in concentrated CaCl₂ solutions. As solute fraction increases, the number of hydrogen bonds formed by hydration water decreases due to increased counter-ion presence, and ion vibrations in the 2–5 THz range intensify, leading to slower ion diffusion. These findings clarify the physical mechanisms underlying ion behavior in concentrated electrolytes and may inform the design of high-performance electrolyte solutions.