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

Abstract

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 H 2 O 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 H 2 O preferred to be dissociated on smithsonite (1 0 1) surface via the interaction of surface Zn with the Ow of H 2 O and H-bond between Hw of H 2 O and surface Os. However, dissociation adsorption and molecular adsorption coexisted on the smithsonite surface at a high coverage rate of H 2 O, and dissociation adsorption remained the main adsorption mechanism. Moreover, we found the interaction between smithsonite surface and H 2 O was weakened as a function of H 2 O coverage, which was because the presence of interlayer H 2 O and different layers of H 2 O decreased the reactivity of the smithsonite surface. The H 2 O is mainly adsorbed on the smithsonite surface by forming three layers of H 2 O (about 10–15 Å), with the ordering degree gradually decreasing.