Registry-Dependent Hydration in Layered Mineral Slit Pores: Insights from Molecular Simulations of Gibbsite and Muscovite.

Interfacial water confined between layered mineral surfaces governs particle aggregation, sliding, and oriented attachment, yet the role of lateral surface registry in controlling hydration remains incompletely understood, particularly across different surface chemistries and hydration states. Here we use molecular dynamics simulations to quantify how translational misalignment between opposing basal surfaces modifies hydration energetics, hydrogen-bonding structure, interaction-energy components, and water mobility in gibbsite and muscovite slit pores over water loadings spanning submonolayer to multilayer regimes. For gibbsite, hydration potential energy is most sensitive to lateral registry at the lowest water loading, whereas the hydration potential-energy landscape becomes progressively flatter as additional water layers form. Hydrogen bond populations vary only modestly with mismatch, and the slab-water and water-water interaction energies are generally only weakly sensitive to mismatch, except at the lowest water loading. At this loading, the two interaction-energy contributions vary in opposite directions, such that changes in one are partially offset by changes in the other. At higher water loadings, both contributions become less sensitive to mismatch, resulting in a comparatively smooth hydration potential-energy response. In muscovite, hydration potential energies exhibit a comparatively weak dependence on lateral mismatch even under monolayer confinement, consistent with strong, ion-dominated hydration of surface-bound K that limits reorganization of confined water with mismatch. Mean-squared displacement analysis further indicates that near-registry alignment generally suppresses lateral water mobility relative to mismatched configurations, most clearly at low loadings. Together, these results identify surface registry as a tunable geometric variable that couples to both the thermodynamics and dynamics of nanoconfined water, while demonstrating that the magnitude and mechanism of registry effects are strongly material- and hydration-state-dependent.