Implementation of a Morse potential to model hydroxyl behavior in phyllosilicates

Area of Science:

• Materials Science
• Computational Chemistry
• Geochemistry

Background:

• Accurate molecular simulation of hydrated clay minerals and phyllosilicates is crucial for understanding their interfaces with aqueous solutions.
• Existing classical force field potentials often struggle to precisely describe the structure and vibrational behavior of these systems.
• Discrepancies in hydroxyl stretch regions of power spectra highlight limitations in current simulation methods.

Purpose of the Study:

• To develop and validate improved classical force field potentials for hydrated clay minerals.
• To enhance the description of structure and vibrational behavior, particularly the O-H bond stretch and hydroxyl orientation.
• To compare simulation results with experimental data and ab initio molecular dynamics.

Main Methods:

• Classical molecular dynamics simulations using the CLAYFF force field.
• Implementation of a new Morse potential for O-H bond stretch, alongside a standard harmonic potential.
• Parametrization of potentials for both dioctahedral and trioctahedral clay phases.
• Comparison of simulation results with experimental measurements and ab initio molecular dynamics.

Main Results:

• Classical and ab initio simulations showed distinct behaviors in the hydroxyl stretch region of power spectra.
• The new Morse potential demonstrated improvements in simulating hydroxyl orientation relative to the clay octahedral sheet.
• Simulations with the improved potentials better reproduced the high-frequency region of the power spectrum for the O-H bond stretch.

Conclusions:

• The developed Morse potential offers a significant improvement over standard harmonic potentials for simulating O-H bond stretch in clay minerals.
• Enhanced classical force fields are essential for accurate molecular simulations of phyllosilicates and their interactions with water.
• These improved potentials will advance the understanding of hydrated clay systems in various scientific disciplines.