Reactive Grand-Canonical Monte Carlo Simulations for Modeling Hydration of MgCl₂

Area of Science:

• Materials Science
• Chemical Engineering
• Computational Chemistry

Background:

• Thermochemical heat storage relies on reversible salt hydration reactions for compact energy devices.
• Predicting equilibrium conditions for complex salts is challenging but crucial for system design.

Purpose of the Study:

• To develop a molecular-level simulation tool for predicting equilibrium conditions in thermochemical heat storage.
• To investigate the hydration behavior of magnesium chloride hydrates.

Main Methods:

• A biased grand-canonical Monte Carlo (GCMC) tool was developed, integrating reactive force field molecular dynamics (ReaxFF).
• The Weeks-Chandler-Andersen (WCA) potential was employed for efficient sampling of trial positions.
• The WCA-ReaxFF-GCMC tool was applied to study the hydration of MgCl2·nH2O.

Main Results:

• Simulation results demonstrated good agreement with experimental and thermodynamic equilibrium data for various hydration levels.
• Observed that water deforms salt surface layers, facilitating further hydration.
• Validated the tool's capability for studying other reactive sorption processes.

Conclusions:

• The WCA-ReaxFF-GCMC tool accurately predicts thermochemical heat storage equilibrium conditions at the molecular level.
• The study provides insights into the mechanism of salt hydration, crucial for material selection and device optimization.
• The developed tool has broader applicability for simulating reactive sorption phenomena.