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ID 118577
Author
Shiraishi, Yui Tokushima University
Kageyama, Maho Tokushima University
Yokoi, Yuu Tokushima University
Kurohama, Saki Tokushima University
Okada, Natsuki Tokushima University
Content Type
Journal Article
Description
The pressure-induced amorphization (PIA) of ice and clathrate hydrates occurs at temperatures significantly below their melting and decomposition points. The PIA of type I clathrate hydrates containing methane and ethane as guest molecules was investigated using Raman and infrared (IR) spectroscopy. With isothermal compression at 100 K, methane hydrate (MH) underwent PIA at 2–3.5 GPa, whereas ethane hydrate (EH) underwent PIA at 4.0–5.5 GPa. The type I clathrate structure consists of small (512) and large (51262) cages. The Raman results revealed that the collapsed small and large cages in the amorphous forms of MH and EH were not distinguishable. The collapsed cages, including the methane and ethane molecules, were similar to the small and large cages, respectively. Their water networks were folded or expanded during the PIA process so that the cavity sizes of the collapsed cages were compatible with those of the guest molecules. Peaks in the IR spectra of crystalline MH assignable to the ro-vibrational transition of methane in large cages were observed in the C–H stretching wavenumber region below 40 K. The ro-vibrational IR band disappeared after amorphization, suggesting that the rotational motion of the methane molecule in the large cage was frozen by the collapse, as reported in previous dielectric spectroscopic and simulation studies. This study contributes to a better understanding of the changes in the local structure around guest molecules during PIA and the dynamics of the guest molecules.
Journal Title
Physical Chemistry Chemical Physics
ISSN
14639076
14639084
NCID
AA11301773
AA11723355
Publisher
The Royal Society of Chemistry
Volume
25
Issue
33
Start Page
22161
End Page
22170
Published Date
2023-08-07
EDB ID
DOI (Published Version)
URL ( Publisher's Version )
FullText File
language
eng
TextVersion
Author
departments
Science and Technology