Implementation of a Morse potential to model hydroxyl behaviorin phyllosilicates

摘要

The accurate molecular simulation of many hydrated chemical systems, including clay minerals andother phyllosilicates and their interfaces with aqueous solutions, requires improved classical forcefield potentials to better describe structure and vibrational behavior. Classical and ab initiomolecular dynamics simulations of the bulk structure of pyrophyllite, talc, and Na-montmorilloniteclay phases exhibit dissimilar behavior in the hydroxyl stretch region of power spectra derived fromatomic trajectories. The classical simulations, using the CLAYFF force field, include either a standardharmonic potential or a new Morse potential parametrized for both dioctahedral and trioctahedralphases for the O–H bond stretch. Comparisons of classical results with experimental values and withab initio molecular dynamics simulations indicate improvements in the simulation of hydroxylorientation relative to the clay octahedral sheet and in the 0–H bond stretch in the high frequencyregion of the power spectrum.