Structural stability of methane hydrate at high pressures

Geoscience Frontiers
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Abstract

The structural stability of methane hydrate under pressure at room temperature was examined by both in-situ single-crystal and powder X-ray diffraction techniques on samples with structure types I, II, and H in diamond-anvil cells. The diffraction data for types II (sII) and H (sH) were refined to the known structures with space groups Fd3m and P63/mmc, respectively. Upon compression, sI methane hydrate transforms to the sII phase at 120 MPa, and then to the sH phase at 600 MPa. The sII methane hydrate was found to coexist locally with sI phase up to 500 MPa and with sH phase up to 600 MPa. The pure sH structure was found to be stable between 600 and 900 MPa. Methane hydrate decomposes at pressures above 3 GPa to form methane with the orientationally disordered Fm3m structure and ice VII (Pn3m). The results highlight the role of guest (CH4)-host (H2O) interactions in the stabilization of the hydrate structures under pressure.

Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Structural stability of methane hydrate at high pressures
Series title Geoscience Frontiers
DOI 10.1016/j.gsf.2010.12.001
Volume 2
Issue 1
Year Published 2011
Language English
Contributing office(s) Eastern Mineral and Environmental Resources Science Center
Description 8 p.
First page 93
Last page 100
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