Stability of doubly occupied N[sub 2] clathrate hydrates investigated by molecular dynamics simulations

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DOIResolve DOI: http://doi.org/10.1063/1.1352078
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TypeArticle
Journal titleThe Journal Of Chemical Physics
Volume114
Issue13
Pages57455754; # of pages: 10
Subjectmolecular dynamics method; organic compounds
AbstractClassical molecular dynamics calculations were performed for a structure II clathrate hydrate with N2 guest molecules in order to investigate the possibility of double occupancy, i.e., two N2 molecules inside one large cage. For all of the pressures, temperatures, and compositions at which the simulations have been performed, the doubly occupied clathrate remained stable. The structure of the host lattice is indistinguishable from that of a singly occupied clathrate hydrate. The volumes and energies are linearly dependent on the filling fraction. The range of values are the same for both the singly as well as doubly occupied clathrates. In the doubly occupied cages, the O–N2 radial distribution function, and therefore the structure in the vicinity of the N2 molecule, is similar to that of the mixed fluid. An extensive investigation of the distances in the cages shows a large similarity between singly and doubly occupied clathrates. All these results indicate that, upon filling the large cages with pairs of molecules, the stresses on the host lattice are comparable to those in single occupation. Small changes in the intermolecular interactions do not affect the results. The clathrate hydrate destabilizes upon increasing the size of the guest molecules by more than about 10%. We also find that the clathrate hydrate remains stable when experimental conditions are closely followed, i.e., for partially doubly occupied clathrates with a pressure dependent filling fraction. The calculated compressibility is the same as in experiments.
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AffiliationNational Research Council Canada; NRC Steacie Institute for Molecular Sciences
Peer reviewedNo
NPARC number12328059
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Record identifier2a08aa1b-d672-4af6-b77b-34ea50934e29
Record created2009-09-10
Record modified2016-05-09
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