Practical considerations for finite concentration molecular dynamics simulations

Area of Science:

• Physical Chemistry
• Computational Chemistry
• Materials Science

Background:

• Understanding concentrated electrolytes is crucial for various applications.
• Existing theories struggle to explain both local hydration and mesoscale assembly.
• Accurate modeling requires accounting for complex ion-solvent interactions.

Purpose of the Study:

• To present an integrated computational workflow, Solvation Characterization via Optimized Probability Ensemble averaging (SCOPE).
• To investigate the speciation and phase behavior of concentrated LiCl(aq) solutions.
• To develop a predictive model for electrolyte solubility and precipitation.

Main Methods:

• Enhanced sampling of single Li+ ion dynamics.
• Reweighting biased trajectories to obtain equilibrium probabilities.
• Chemical-potential correction for finite-size simulation effects.

Main Results:

• Identified distinct ion organization regimes: solvated ions, contact ion pairs, and aggregated clusters.
• Observed a shift from solvated ions at low concentrations to Li-xCl clusters at the solubility limit.
• Accurately predicted temperature-dependent solubility and clarified precipitation mechanisms.

Conclusions:

• SCOPE provides a transferable strategy for studying concentrated liquid systems.
• The findings offer a fundamental organizing principle for electrolyte behavior.
• This work advances the understanding of speciation and phase transitions in complex solutions.