Open AccessTransformations in methane hydrates
Author(s) -
I−Ming Chou,
Anurag Sharma,
Robert C. Burruss,
Jinfu Shu,
Hokwang Mao,
Russell J. Hemley,
Alexander F. Goncharov,
Laura A. Stern,
Stephen H. Kirby
Publication year - 2000
Publication title -
proceedings of the national academy of sciences of the united states of america
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.011
H-Index - 771
eISSN - 1091-6490
pISSN - 0027-8424
DOI - 10.1073/pnas.250466497
Subject(s) - methane , hydrate , clathrate hydrate , microprobe , raman spectroscopy , electron microprobe , crystal structure , phase (matter) , chemistry , mineralogy , natural gas , crystallography , materials science , chemical engineering , organic chemistry , physics , optics , engineering
Detailed study of pure methane hydrate in a diamond cell within 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 ofa = 17.158(2) Å and volumeV = 5051.3(13) Å3 ; structure H at 600 MPa has a hexagonal unit cell ofa = 11.980(2) Å,c = 9.992(3) Å, andV = 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.