Closest-Packing Water Monolayer Stably Intercalated in Phyllosilicate Minerals under High Pressure

Abstract

The directional hydrogen-bond (HB) network and nondirectional van der Waals (vdW) interactions make up the specificity of water. Directional HBs could construct an ice-like monolayer in hydrophobic confinement even in the ambient regime. Here, we report a water monolayer dominated by vdW interactions confined in a phyllosilicate interlayer under high pressure. Surprisingly, it was in a thermodynamically stable state coupled with bulk water at the same pressure (P) and temperature (T), as revealed by the thermodynamic integration approach on the basis of molecular dynamics (MD) simulations. Both classical and ab initio MD simulations showed water O atoms were stably trapped and exhibited an ordered hexagonal closest-packing arrangement, but OH bonds of water reoriented frequently and exhibited a specific two-stage reorientation relaxation. Strikingly, hydration in the interlayer under high pressure had no relevance with surface hydrophilicity rationalized by the HB forming ability, which, however, determines wetting in the ambient regime. Intercalated water molecules were trapped by vdW interactions, which shaped the closest-packing arrangement and made hydration energetically available. The high pressure–volume term largely drives hydration, as it compensates the entropy penalty which is restricted by a relatively lower temperature. This vdW water monolayer should be ubiquitous in the high pressure but low-temperature regime.

Insights into Carbon Dioxide Hydrate Nucleation on the External Basal Surface of Clay Minerals from Molecular Dynamics Simulations

“…The basic layers of Mnt and Ilt models were based on the structure of pyrophyllite . These structures have been reliably verified in other simulation studies. − …”

Percolation of Low‐Dimensional Water at Crystalline Interfaces Mediates Fluid Migration in Subducting Slabs

“…Nevertheless, they reveal that for a crystalline interface that does not form hydrogen bonds well, pressure‐induced water intercalation is anticipated. Pressure‐induced water intercalation has also been observed in talc and kaolinite interlayers (Chen, Zhou, Zhu, Lu, & He, 2020; Chinnery et al., 1999; Fumagalli et al., 2001; Hwang et al., 2017). Our previous simulation study of talc and kaolinite with multiple crystalline layers stacking under a periodic boundary condition showed that water can be intercalated when pressure is high (Chen, Zhou, Zhu, Lu, & He, 2020).…”

“…Hydroxyl groups on the talc surface with Si vacancies, were thought to be the reason for interlayer hydration, as the increased hydrophilicity with the addition of hydroxyl groups was intuitively thought to favor water intercalation. However, our previous study showed that Si vacancies are not necessary for interlayer hydration (Chen, Zhou, Zhu, Lu, & He, 2020). A crystalline interface with hydrophobic surfaces favors water intercalation at high pressure, which, although counterintuitive, can be justified by the volume‐loss effect.…”

“…Researchers have considered phyllosilicates with intercalated water to be hydrous mineral phases, which serve as water carriers in the descending slab (Chinnery et al., 1999; Fumagalli et al., 2001; Hwang et al., 2017; Ohtani, 2005, 2015). However, as shown by our thermodynamic study based on atomic simulations, the intercalated water layer is stable only when the water activity of the coexisting fluid is sufficiently high (Chen, Zhou, Zhu, Lu, & He, 2020). In other words, if the fluid is drained, water in the interlayer is expelled.…”

How clay delamination supports aseismic slip

“…μ i and μ f at certain temperature and pressure conditions are derived with TI through decoupling interactions between a water molecule and surrounding environment, which can be found in our previous studies (Chen et al 2020a;Chen et al 2020b;Zhou et al 2020) and briefly introduced in Section S2 of the Supplemental Material.…”