A Coarse-Grained Interaction Model for Sodium Dominant Montmorillonite.

Area of Science:

• Materials Science
• Nanotechnology
• Computational Chemistry

Background:

• Montmorillonite, a key component of bentonite, exhibits nanoscale absorbent and swelling properties due to electrical double-layer interactions.
• These nanoscale phenomena significantly alter the macroscopic transport properties of clay.
• Bridging nanoscale processes and macroscale properties requires mesoscale models that detail the clay's pore network.

Purpose of the Study:

• To develop a coarse-grained (CG) mesoscale model for sodium montmorillonite.
• To link nanoscale physical chemistry to the macroscopic transport properties of bentonite clay.
• To provide a computational tool for simulating clay behavior at the hundreds-to-thousands of nanometers scale.

Main Methods:

• Developed a CG mesoscale model representing montmorillonite platelets with central and edge particles.
• Optimized two-body potentials using all-atom molecular dynamics simulations and potential mean force calculations.
• Validated the model through scalability tests, reproduction of literature potentials, and comparison of simulated to experimental elastic properties.

Main Results:

• The CG model successfully represents sodium montmorillonite at the mesoscale.
• Simulated elastic properties of 1000 Na montmorillonite platelets closely matched experimental bentonite elastic properties.
• The model demonstrates good scalability and reproduces known potentials of mean force.

Conclusions:

• The developed CG mesoscale model is a viable tool for simulating sodium montmorillonite.
• The model effectively links nanoscale interactions to macroscopic properties like elasticity.
• This approach overcomes limitations of all-atom simulations for mesoscale clay modeling.