Natural Gas Hydrates: Structure II
Steven Dutch, Professor Emeritus, Natural and Applied Sciences, Universityof Wisconsin - Green BayType II structure is cubic. In addition to pentagonal dodecahedra,hydrocarbons are also enclosed by polyhedra with 4 hexagonal and 12 pentagonalfaces (of course somewhat distorted. The polyhedron has tetrahedral symmetry andis shown below in a number of orientations.
Clusters of these solids link tetrahedrally by sharing faces.
The voids between three 16-faced solids are filled by triads of dodecahedra(of course, to join this way, the dodecahedra must also be slightly distorted,since the dihedral angle of a true pentagonal dodecahedron is only 116.5degrees, not 120 degrees)
The result is that tetrahedral clusters of 16-faced polyhedra (below, left)are surrounded by cages of dodecahedra (below right).
Below are views of a cluster of 16-faced polyhedra and a cluster withenclosing dodecahedra, viewed along a 4-fold inversion axis.
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