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Molecular hydrogen occupancy in binary THF-H2 clathrate hydrates by high resolution neutron diffraction.
Keith C Hester1, Timothy A Strobel, E Dendy Sloan
1Center for Hydrate Research, Colorado School of Mines, Golden, CO 80401, USA.
The Journal of Physical Chemistry. B
|July 21, 2006
Summary
Researchers studied hydrogen filling in tetrahydrofuran clathrate hydrates using neutron diffraction. Hydrogen molecules singly occupied small cavities under pressure, clarifying previous findings in this binary hydrate system.
Area of Science:
- Materials Science
- Chemical Physics
- Crystallography
Background:
- Clathrate hydrates are inclusion compounds with cage-like structures.
- Understanding guest molecule occupancy is crucial for hydrate applications.
- Previous studies showed discrepancies in hydrogen occupancy in binary hydrate systems.
Purpose of the Study:
- To determine the time-space average filling of hydrogen molecules in a binary tetrahydrofuran (THF)-d(8) + D(2) sII clathrate hydrate.
- To elucidate the localization and occupancy of hydrogen within the clathrate lattice structure.
Main Methods:
- High-resolution neutron diffraction was employed to analyze the clathrate hydrate structure.
- Experiments were conducted at low temperatures (20 K) and high pressures (70 MPa).
Main Results:
- Hydrogen molecules were observed to fill the small dodecahedral cavities of the sII clathrate hydrate.
- The nuclear density of hydrogen was approximately spherically distributed and centered within the cavities.
- At 70 MPa, molecular hydrogen was found to singly occupy the sII small cavity.
Conclusions:
- The study clarifies the occupancy of molecular hydrogen in THF-d(8) + D(2) clathrate hydrates.
- The findings help resolve discrepancies regarding hydrogen occupancy in binary hydrate systems.
- This research provides insights into guest molecule behavior within clathrate cage structures.