title: Observation of interstitial molecular hydrogen in clathrate hydrates.
abstract: The current knowledge and description of guest molecules within clathrate hydrates only accounts for occupancy within regular polyhedral water cages. Experimental measurements and simulations, examining the tert-butylamine + H2 + H2O hydrate system, now suggest that H2 can also be incorporated within hydrate crystal structures by occupying interstitial sites, that is, locations other than the interior of regular polyhedral water cages. Specifically, H2 is found within the shared heptagonal faces of the large (4(3)5(9)6(2)7(3)) cage and in cavities formed from the disruption of smaller (4(4)5(4)) water cages. The ability of H2 to occupy these interstitial sites and fluctuate position in the crystal lattice demonstrates the dynamic behavior of H2 in solids and reveals new insight into guest-guest and guest-host interactions in clathrate hydrates, with potential implications in increasing overall energy storage properties.
authors.affiliation: Department of Chemical and Biological Engineering, Colorado School of Mines, 1500 Illinois Street, Golden, CO 80401 (USA).
authors.forename: R Gary
authors.initials: RG
authors.lastname: Grim
authors.forename: Brian C
authors.initials: BC
authors.lastname: Barnes
authors.forename: Patrick G
authors.initials: PG
authors.lastname: Lafond
authors.forename: Winfred A
authors.initials: WA
authors.lastname: Kockelmann
authors.forename: David A
authors.initials: DA
authors.lastname: Keen
authors.forename: Alan K
authors.initials: AK
authors.lastname: Soper
authors.forename: Masaki
authors.initials: M
authors.lastname: Hiratsuka
authors.forename: Kenji
authors.initials: K
authors.lastname: Yasuoka
authors.forename: Carolyn A
authors.initials: CA
authors.lastname: Koh
authors.forename: Amadeu K
authors.initials: AK
authors.lastname: Sum
keywords: Raman spectroscopy; density functional calculations; inclusion compounds; molecular dynamics; neutron diffraction