Interfacial water structure plays an important role in many geochemical reactions including ion adsorption and desorption and mineral dissolution and precipitation. We explored how the surface charge and crystal type can influence the structure of the interfacial hydration layers by using in situ high-resolution X-ray reflectivity (XR) combined with fully atomistic molecular dynamics (MD) simulations. The (001) surface of ionic crystal barite (BaSO<sub>4</sub>), that is stoichiometrically charge neutral, has the primary hydration layer in which adsorbed water molecules mimic the lattice structure of the crystallographic plane [1]. In contrast, the (001) surface of phyllosilicate muscovite mica, that has a negative charge, can have distinct hydration layers whose molecular arrangements vary depending on the hydration strength of adsorbed counter ions [2]. The similarities and differences between the XR and MD results will be discussed to evaluate the uniqueness of the structural model obtained from XR analyses and the accuracy of the force field used in MD simulations.

Hydration structure at mineral–water interfaces

2019 Fall National Meeting

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