Dynamical and energetic properties of hydrogen and hydrogen–tetrahydrofuran clathrate hydrates

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Title: Dynamical and energetic properties of hydrogen and hydrogen–tetrahydrofuran clathrate hydrates
Authors: Gorman, Paul D.
English, Niall J.
MacElroy, J. M. Don
Permanent link: http://hdl.handle.net/10197/3385
Date: 3-Oct-2011
Abstract: Classical equilibrium molecular dynamics (MD) simulations have been performed to investigate the dynamical and energetic properties in hydrogen and mixed hydrogen-tetrahydrofuran sII hydrates at 30 and 200K and 0.05 kbar, and also at intermediate temperatures, using SPC/E and TIP4P-2005 water models. The potential model is found to have a large impact on overall density, with the TIP4P-2005 systems being on average 1 % more dense than their SPC/E counterparts, due to the greater guest-host interaction energy. For the lightly-filled mixed H2-THF system, in which there is single H2 occupation of the small cage (1s1l), we find that the largest contribution to the interaction energy of both types of guest is the van der Waals component with the surrounding water molecules in the constituent cavities. For the more densely-filled mixed H2-THF system, in which there is double H2 occupation in the small cage (2s1l), we find that there is no dominant component (i.e., van der Waals or Coulombic) in the H2 interaction energy with the rest of the system, but for the THF molecules, the dominant contribution is again the van der Waals interaction with the surrounding cage-water molecules; again, the Coulombic component increases in importance with increasing temperature. The lightly-filled pure H2 hydrate (1s4l) system exhibits a similar pattern vis-à-vis the H2 interaction energy as for the lightly-filled mixed H2-THF system, and for the more densely-filled pure H2 system (2s4l), there is no dominant component of interaction energy, due to the multiple occupancy of the cavities. By consideration of Kubic harmonics, there is some evidence of preferential alignment of the THF molecules, particularly at 200 K; this was found to arise at higher temperatures due to transient hydrogen bonding of the oxygen atom in THF molecules with the surrounding cage-water molecules.
Funding Details: Science Foundation Ireland
Other funder
Type of material: Journal Article
Publisher: RSC publications
Journal: Physical Chemistry Chemical Physics
Volume: 13
Issue: 13
Start page: 19780
End page: 19787
Copyright (published version): 2011 the Owner Societies
Keywords: Molecular dynamicsEnergetic propertiesHydrogen hydrateTHF hydrateDynamical properties
Subject LCSH: Molecular dynamics
Tetrahydrofuran--Properties
Hydrogen--Properties
Hydrates--Properties
DOI: 10.1039/C1CP21882D
Other versions: http://dx.doi.org/10.1039/C1CP21882D
Language: en
Status of Item: Peer reviewed
Appears in Collections:Solar Energy Conversion (SEC) Cluster Research Collection
Chemical and Bioprocess Engineering Research Collection

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