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Title: Phase Behavior of H[subscript 2] + H[subscript 2]O at High Pressures and Low Temperatures

Abstract

Whereas several clathrate-like structures are known to exist from mixtures of H{sub 2} + H{sub 2}O under pressure, the combined high-pressure and low-temperature region of the phase diagram remains largely unexplored. Here we report a combined Raman spectroscopy and synchrotron X-ray diffraction study on the low-temperature region of the phase diagram. Below 120 K, the H{sub 2} vibron originating from the clathrate 2 (C{sub 2}) phase splits into two distinct components, yet X-ray diffraction measurements reveal no structural change between room temperature and 11 K. We suggest that the two vibrons of the C{sub 2} phase at low temperature originate from vibrational transitions of hydrogen molecules in the ground and first excited rotational energy levels. At 1 GPa we observe the clathrate 1 (C{sub 1}) phase to persist to the lowest temperature measured (80 K). Upon decompression from the C{sub 2} phase we observed the appearance of cubic ice (I{sub c}), which converted to a new phase before transforming to the C{sub 1} phase. The structure of the new phase is consistent with a water framework similar to {alpha}-quartz; the structure could also be related to the tetragonal clathrate phase reported previously for nitrogen and argon guests.

Authors:
; ;  [1]
  1. (CIW)
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
Sponsoring Org.:
NSFDOE - BASIC ENERGY SCIENCESNNSA
OSTI Identifier:
1021793
Resource Type:
Journal Article
Journal Name:
J. Phys. Chem. C
Additional Journal Information:
Journal Volume: 115; Journal Issue: (11) ; 03, 2011; Journal ID: ISSN 1932-7447
Country of Publication:
United States
Language:
ENGLISH
Subject:
08 HYDROGEN; ARGON; CLATHRATES; ENERGY LEVELS; HYDROGEN; MIXTURES; NITROGEN; PHASE DIAGRAMS; RAMAN SPECTROSCOPY; SYNCHROTRONS; WATER; X-RAY DIFFRACTION

Citation Formats

Strobel, Timothy A., Somayazulu, Maddury, and Hemley, Russell J. Phase Behavior of H[subscript 2] + H[subscript 2]O at High Pressures and Low Temperatures. United States: N. p., 2011. Web. doi:10.1021/jp1122536.
Strobel, Timothy A., Somayazulu, Maddury, & Hemley, Russell J. Phase Behavior of H[subscript 2] + H[subscript 2]O at High Pressures and Low Temperatures. United States. doi:10.1021/jp1122536.
Strobel, Timothy A., Somayazulu, Maddury, and Hemley, Russell J. Tue . "Phase Behavior of H[subscript 2] + H[subscript 2]O at High Pressures and Low Temperatures". United States. doi:10.1021/jp1122536.
@article{osti_1021793,
title = {Phase Behavior of H[subscript 2] + H[subscript 2]O at High Pressures and Low Temperatures},
author = {Strobel, Timothy A. and Somayazulu, Maddury and Hemley, Russell J.},
abstractNote = {Whereas several clathrate-like structures are known to exist from mixtures of H{sub 2} + H{sub 2}O under pressure, the combined high-pressure and low-temperature region of the phase diagram remains largely unexplored. Here we report a combined Raman spectroscopy and synchrotron X-ray diffraction study on the low-temperature region of the phase diagram. Below 120 K, the H{sub 2} vibron originating from the clathrate 2 (C{sub 2}) phase splits into two distinct components, yet X-ray diffraction measurements reveal no structural change between room temperature and 11 K. We suggest that the two vibrons of the C{sub 2} phase at low temperature originate from vibrational transitions of hydrogen molecules in the ground and first excited rotational energy levels. At 1 GPa we observe the clathrate 1 (C{sub 1}) phase to persist to the lowest temperature measured (80 K). Upon decompression from the C{sub 2} phase we observed the appearance of cubic ice (I{sub c}), which converted to a new phase before transforming to the C{sub 1} phase. The structure of the new phase is consistent with a water framework similar to {alpha}-quartz; the structure could also be related to the tetragonal clathrate phase reported previously for nitrogen and argon guests.},
doi = {10.1021/jp1122536},
journal = {J. Phys. Chem. C},
issn = {1932-7447},
number = (11) ; 03, 2011,
volume = 115,
place = {United States},
year = {2011},
month = {9}
}