Natural Gas Hydrates: Structure I

Steven Dutch, Natural and Applied Sciences, University of Wisconsin - Green Bay
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Structure I is cubic (diploidal). Pentagonal cages of water molecules enclosing a methane molecule occupy the corners of the unit cell, and a rotated cage occupies the center (left above). Other water molecules link the dodecahedra, forming hexagonal rings (right, above).

The interstices between the dodecahedra are occupied by cages with hexagonal ends and 12 pentagonal faces. Some of the pentagonal faces are shared with dodecahedra, others with 14-faced cages. The hexagonal rings joining the dodecahedra are also ends of the 14-faced cages. These cages join end to end to form columns, which share faces with intervening perpendicular columns. Two sets of columns are shown above.

In the diagram above, we see the third set of columns perpendicular to the other 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 above is shown.

References

Henriet, J.-P., Mienert, J., 1998; Gas hydrates : relevance to world margin stability and climate change, London : The Geological Society, Geological Society 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; New York Academy of Sciences. New York, NY, United States. Pages: 1039.

Paull, Charles K. (editor); Dillon, William P. (editor), 2000; Natural gas hydrates; 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 or pipe 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 natural gas 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 14 Dec 2009

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