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Phys. Rev. Lett. 93, 125503 (2004) [4 pages]

Structure and Dynamics of Hydrogen Molecules in the Novel Clathrate Hydrate by High Pressure Neutron Diffraction

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Konstantin A. Lokshin1 *, Yusheng Zhao1, Duanwei He1, Wendy L. Mao2,3, Ho-Kwang Mao2, Russell J. Hemley2, Maxim V. Lobanov4, and Martha Greenblatt4
1LANSCE-12, Los Alamos National Laboratory, Los Alamos, New Mexico 87544, USA
2Geophysical Laboratory, Carnegie Institution of Washington, Washington, D.C. 20015, USA
3Department of the Geophysical Sciences, University of Chicago, Chicago, Illinois 60637, USA
4Department of Chemistry and Chemical Biology, Rutgers University, Piscataway, New Jersey 08854, USA

Received 17 February 2004; published 14 September 2004

The D2 clathrate hydrate crystal structure was determined as a function of temperature and pressure by neutron diffraction for the first time. The hydrogen occupancy in the (32+X)H2·136H2O, x=0-16 clathrate can be reversibly varied by changing the large (hexakaidecahedral) cage occupancy between two and four molecules, while remaining single occupancy of the small (dodecahedral) cage. Above 130–160 K, the guest D2 molecules were found in the delocalized state, rotating around the centers of the cages. Decrease of temperature results in rotation freezing followed by a complete localization below 50 K.


©2004 The American Physical Society

URL: http://link.aps.org/abstract/PRL/v93/e125503
DOI: 10.1103/PhysRevLett.93.125503
PACS: 61.66.–f, 61.12.–q

* Correspondence and requests for materials should be addressed to K. L. (e-mail: lokshin@lanl.gov).

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