Interfaces involving aqueous fluid phases play critical roles in natural and technologically important systems. Atomic-scale details including structure, energetics, speciation, and dynamics are essential to understanding and manipulating their chemical and physical properties at the interfaces for applications in energy and environment. Using molecular dynamic simulations and CLAFF forcefield, the interlayer hydration energy and vibrational density of state of hydrotalcite are correlated to the swelling, which involves layer-by-layer hydration. The interlayer hydration in talc leads to a double-hydrated 10 Å phase and a two-dimensional ice-like phase at high pressure. Molecular modeling suggests that the water adsorption at the muscovite (001) surface is controlled by the surface lattice structure. Hydration at the calcite and kerogen surfaces significantly affect the desorption free energy of oil molecular clusters from the surfaces and oil wettability of the surfaces. Using first-principles molecular dynamics simulations, grain boundary hydration of forsterite (Mg2SiO4) and pyrochlore (Gd2Ti2O7) results in the dissociation of water molecules and presence of hydroxide and hydronium species, in addition to molecular water within the grain boundaries. Negative enthalpy of forsterite grain boundary hydration provides the energetic driving force for the greater relative stability of hydrous grain boundaries with respect to corresponding anhydrous ones. Transports of hydrogen and oxygen within the grain boundaries have distinct mechanisms coupled by finite lifetimes of the shared speciation. Examples are used to highlight that technology improvement is critical in experimental verifications of theoretical modeling results.

Molecular modeling of mineral-fluid interactions: Hydration of interlayer, surface, and grain boundaries

ACS Fall 2021

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