Transformations in methane hydrates

Detailed study of pure methane hydrate in a diamond cell with in situ optical, Raman, and x-ray microprobe techniques reveals two previously unknown structures, structure II and structure H, at high pressures. The structure II methane hydrate at 250 MPa has a cubic unit cell of a = 17.158(2) Å and v...

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Bibliographic Details
Main Authors: Chou, I-Ming, Sharma, Anurag, Burruss, Robert C., Shu, Jinfu, Mao, Ho-kwang, Hemley, Russell J., Goncharov, Alexander F., Stern, Laura A., Kirby, Stephen H.
Format: Text
Language:English
Published: The National Academy of Sciences 2000
Subjects:
Physical Sciences
Methane hydrate
Online Access:http://www.ncbi.nlm.nih.gov/pmc/articles/PMC17601
http://www.ncbi.nlm.nih.gov/pubmed/11087836
Description
Summary:Detailed study of pure methane hydrate in a diamond cell with in situ optical, Raman, and x-ray microprobe techniques reveals two previously unknown structures, structure II and structure H, at high pressures. The structure II methane hydrate at 250 MPa has a cubic unit cell of a = 17.158(2) Å and volume V = 5051.3(13) Å3; structure H at 600 MPa has a hexagonal unit cell of a = 11.980(2) Å, c = 9.992(3) Å, and V = 1241.9(5) Å3. The compositions of these two investigated phases are still not known. With the effects of pressure and the presence of other gases in the structure, the structure II phase is likely to dominate over the known structure I methane hydrate within deep hydrate-bearing sediments underlying continental margins.

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