Neutron scattering measurements and computation of the quantum dynamics of hydrogen molecules trapped in the small and large cages of clathrate hydrates

Daniele Colognesi, Milva Celli, Lorenzo Ulivi, Minzhong Xu, Zlatko Bacic

Research output: Contribution to journalArticle

Abstract

We report inelastic neutron scattering (INS) measurements on molecular hydrogen trapped in simple (D2O) and binary (D2O plus perdeuterated tetrahydrofuran) clathrate hydrates, performed at a low temperature using two different neutron spectrometers to probe both energy and momentum transfer. The INS spectra of binary clathrate samples exhibit a rich structure containing sharp bands arising from both the rotational transitions and the rattling modes of the guest H2 molecule. They agree well with the rigorous fully quantum simulations, which account for the subtle effects of the anisotropy, angular and radial, of the host cage on the H2 microscopic dynamics and the resulting spectra. The simple clathrate samples present a much greater challenge, due to the multiple H2 occupancy of the large cages, which makes the quantum calculations an extremely difficult task. In addition, we discuss in detail various physical aspects of the experimental and simulated INS spectra, such as their temperature dependence, the effects of the cage geometry, and the different features associated with the ortho-hydrogen and para-hydrogen species.

Original languageEnglish (US)
Pages (from-to)7314-7326
Number of pages13
JournalJournal of Physical Chemistry A
Volume117
Issue number32
DOIs
StatePublished - Aug 15 2013

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Inelastic neutron scattering
clathrates
Neutron scattering
Hydrates
hydrates
Hydrogen
inelastic scattering
neutron scattering
Molecules
hydrogen
ortho hydrogen
Neutron spectrometers
para hydrogen
molecules
neutron spectrometers
Momentum transfer
tetrahydrofuran
Energy transfer
momentum transfer
Anisotropy

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry

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Neutron scattering measurements and computation of the quantum dynamics of hydrogen molecules trapped in the small and large cages of clathrate hydrates. / Colognesi, Daniele; Celli, Milva; Ulivi, Lorenzo; Xu, Minzhong; Bacic, Zlatko.

In: Journal of Physical Chemistry A, Vol. 117, No. 32, 15.08.2013, p. 7314-7326.

Research output: Contribution to journalArticle

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