Natural Gas Hydrates: Structure I
Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green Bay
Structure I is cubic (diploidal). Pentagonal cages of water moleculesenclosing a methane molecule occupy the corners of the unit cell, and a rotatedcage occupies the center (left above). Other water molecules link thedodecahedra, forming hexagonal rings (right, above).
The interstices between the dodecahedra are occupied by cages with hexagonalends and 12 pentagonal faces. Some of the pentagonal faces are shared withdodecahedra, others with 14-faced cages. The hexagonal rings joining thedodecahedra are also ends of the 14-faced cages. These cages join end to end toform columns, which share faces with intervening perpendicular columns. Two setsof columns are shown above.
In the diagram above, we see the third set of columns perpendicular to theother two sets.
In the diagram above, we see the 14-faced cages of a unit cell. These fit between the dodecahedral cages.
The diagram above shows the dodecahedra at the corners of a unit cell together with the intervening 14-faced cages. The rotated dodecahedron at the center of the unit cell is concealed, but its counterpart in the next cell aboveis shown.
References
Henriet, J.-P., Mienert, J., 1998; Gas hydrates : relevance to world marginstability and climate change, London : The Geological Society, GeologicalSociety special publication no. 137, 338 p.
Kleinberg, Robert; Brewer, Peter, 2001; Probing gas hydrate deposits. American Scientist. vol. 89; no. 3, Pages 244-251.
Holder, Gerald-D (editor); Bishnoi, P. R. (editor), 2000; Gas hydrates;challenges for the future. Annals of the New York Academy of Sciences. 912; NewYork Academy of Sciences. New York, NY, United States. Pages: 1039.
Paull, Charles K. (editor); Dillon, William P. (editor), 2000; Natural gashydrates; occurrence, distribution, and detection. Geophysical Monograph 124,American Geophysical Union. Washington, D.C., United States. Pages: 315.
Haq, Bilal U., 1998; Gas hydrates; greenhouse nightmare? Energy panacea orpipe dream? GSA Today. vol. 8; 11, Pages 1-6. Geological Society of America(GSA). Boulder, CO, United States
Smelik, Eugene A.; King, H. E. Jr., 1997; Crystal-growth studies of naturalgas clathrate hydrates using a pressurized optical cell. American Mineralogist.vol. 82; 1-2, Pages 88-98. Mineralogical Society of America. Washington, DC,United States.
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Created 1 August 2003, Last Update