期刊
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
卷 109, 期 52, 页码 21240-21245出版社
NATL ACAD SCIENCES
DOI: 10.1073/pnas.1213342110
关键词
bilayer water and ice; molecular dynamics simulation; bilayer methane hydrate; amorphous-to-amorphous transition
资金
- National Science Foundation [CBET-1036171, CBET-1066947]
- Army Research Laboratory [W911NF1020099]
- Nebraska Research Initiative
- University of Nebraska Holland Computing Center
- Directorate For Engineering
- Div Of Chem, Bioeng, Env, & Transp Sys [1066947] Funding Source: National Science Foundation
A distinctive physical property of bulk water is its rich solid-state phase behavior, which includes 15 crystalline (ice I-ice XIV) and at least 3 glassy forms of water, namely, low-density amorphous, high-density amorphous, and very-high-density amorphous (VHDA). Nanoscale confinement adds a new physical variable that can result in a wealth of new quasi-2D phases of ice and amorphous ice. Previous computer simulations have revealed that when water is confined between two flat hydrophobic plates about 7-9 angstrom apart, numerous bilayer (BL) ices (or polymorphs) can arise [e. g., BL-hexagonal ice (BL-ice I)]. Indeed, growth of the BL-ice I through vapor deposition on graphene/Pt(111) substrate has been achieved experimentally. Herein, we report computer simulation evidence of pressure-induced amorphization from BL-ice I to BL-amorphous and then to BL-VHDA(2) at 250 K and 3 GPa. In particular, BL-VHDA(2) can transform into BL-VHDA(1) via decompression from 3 to 1.5 GPa at 250 K. This phenomenon of 2D polyamorphic transition is akin to the pressure- induced amorphization in 3D ice (e. g., from hexagonal ice to HDA and then to VHDA via isobaric annealing). Moreover, when the BL-ice I is compressed instantly to 6 GPa, a new very-high-density BL ice is formed. This new phase of BL ice can be viewed as an array of square ice nanotubes. Insights obtained from pressure-induced amorphization and crystallization of confined water offer a guide with which to seek a thermodynamic path to grow a new form of methane clathrate whose BL ice framework exhibits the Archimedean 4.8(2) (square-octagon) pattern.
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