Abstract
The 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 , 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 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.
- Received 17 February 2004
DOI:https://doi.org/10.1103/PhysRevLett.93.125503
©2004 American Physical Society