Solvation structures and ion dynamics of CaCl2 aqueous electrolytes using metadynamics and machine learning molecular dynamics simulations

Abstract

This study uses ab initio and machine learning-based molecular dynamics simulations to explore solvation structures and ion dynamics in CaCl₂ aqueous electrolytes. We identify multiple solvation structures around Ca²⁺ ions, influencing water molecule orientation extending to second hydration shell and residence times of water molecules in first hydration shell. The self-diffusivities of ions and water molecules, as calculated in machine learning-based molecular dynamics simulations, closely align with experimental measurements. Additionally, we analyze Ca²⁺ ion transitions across ballistic, subdiffusive, and diffusive regimes by analyzing angle distribution histograms and van Hove correlation function, providing a comprehensive understanding of the underlying molecular interactions.