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Rich Phase Behavior of Two-Dimensional Water under Nanoconfinement and High Pressure Conditions
Abstract
Water confined in nanopores is ubiquitous in geological and biological environments, as well as in engineering settings. Understanding the phase behavior of nanoconfined water under high pressure conditions has broad implications in both fundamental science and applied technology. The extreme nanoscale confinement can not only alter the dynamic transport behavior of liquid water, but also lead to new low-dimensional ice phases not seen in the bulk. Over the past three decades, water structures under nanoscale confinement have been widely explored through computer simulations and experiments. Despite these efforts, the understanding of the phase behavior of nanoconfined water is still largely incomplete, especially at extreme conditions (ultrahigh pressures and high temperatures), owing to the challenges faced by the experimental detection of the corresponding systems.Herein, we report ab initio molecular simulation-based evidence of the exceptionally rich phase behavior of monolayer/bilayer/trilayer ice under nanoconfinement and high pressures. The newly predicted two-dimensional structures included six molecular, two plastic (one being monolayer hexatic ice), two partially ionic (PII), and five superionic (SI) ice phases, as well as a sliding superionic ice (sSI) structure. A flat zigzag ice chain (ZZMI) and a bilayer ice VII-like structure (BL-iVII) were observed to form spontaneously without obeying the well-known ice rule. Moreover, we found that symmetry breaking of the underlying hydrogen bonding network in the BL-iVII plays a key role in the rich phase behavior of this new family of two-dimensional ices. Importantly, the two-dimensional PII (at ~ 10 GPa) and SI (from 2.5 to 20.0 GPa) phases could be potentially produced in the laboratory at orders-of-magnitude lower pressures compared to those required for the bulk PII (> 1400 GPa) or SI (> 56 GPa) phases. In addition, the simulations predicted the formation of a previously unreported SI phase (sSI, found neither in bulk nor low-dimensional SIs), whose ice layers could slip relatively freely in the lateral direction.
Subject Area
Physical chemistry
Recommended Citation
Jiang, Jian, "Rich Phase Behavior of Two-Dimensional Water under Nanoconfinement and High Pressure Conditions" (2022). ETD collection for University of Nebraska-Lincoln. AAI29165510.
https://digitalcommons.unl.edu/dissertations/AAI29165510