Hydration mechanisms of smithsonite from DFT-D calculations and MD simulations

Investigation on the mineral-water interactions is crucial for understanding the subsequent interfacial reactions. Currently, the hydration mechanisms of smithsonite are still obscure. In this paper, the adsorption of H2O at different coverage rates on smithsonite (1 0 1) surface was innovatively investigated using density-functional theory (DFT) calculations and molecular dynamics (MD) simulations by analyzing adsorption model, interaction energy, atomic distance, density of state, electron density difference, concentration profile, radial distribution function and self-diffusion coefficient. We found that single H2O preferred to be dissociated on smithsonite (1 0 1) surface via the interaction of surface Zn with the Ow of H2O and H-bond between Hw of H2O and surface Os. However, dissociation adsorption and molecular adsorption coexisted on the smithsonite surface at a high coverage rate of H2O, and dissociation adsorption remained the main adsorption mechanism. Moreover, we found the interaction between smithsonite surface and H2O was weakened as a function of H2O coverage, which was because the presence of interlayer H2O and different layers of H2O decreased the reactivity of the smithsonite surface. The H2O is mainly adsorbed on the smithsonite surface by forming three layers of H2O (about 10-15 angstrom), with the ordering degree gradually decreasing. (c) 2022 Published by Elsevier B.V. on behalf of China University of Mining & Technology.

Automated summary

This study investigated the adsorption of water on the smithsonite surface using theoretical calculations and simulations. It was found that single water molecules preferentially dissociate on the surface, while both dissociation and molecular adsorption coexist at high coverage rates. The interaction between the smithsonite surface and water weakens with increasing water coverage, and water molecules mainly adsorb in three layers on the surface.