title: Diffusive hydrogen inter-cage migration in hydrogen and hydrogen-tetrahydrofuran clathrate hydrates.
abstract: Classical equilibrium molecular dynamics simulations have been performed to investigate the diffusive properties of inter-cage hydrogen migration in both pure hydrogen and mixed hydrogen-tetrahydrofuran sII hydrates at 0.05 kbar from 200 K and up to 250-260 K. For mixed H2-THF systems in which there is single H2 occupation of the small cage (labelled "1S1L"), we found that no H2 migration occurs. However, for more densely filled H2-THF and pure-H2 systems, in which there is more than single H2 occupation in the small cage, there is an onset of inter-cage H2 migration events from the small cages to neighbouring cavities at around 200 K. The mean square displacements of the hydrogen molecules were fitted to a mathematical model consisting of an anomalous term and a Fickian component, and nonlinear regression fitting was conducted to estimate long-time (inter-cage) diffusivities. An approximate Arrhenius temperature relationship for the diffusion coefficient was examined and an estimation of the hydrogen hopping energy barrier was calculated for each system.
authors.affiliation: The SFI Strategic Research Cluster in Solar Energy Conversion, School of Chemical and Bioprocess Engineering, University College Dublin, Belfield, Dublin 4, Ireland.
authors.forename: Huayu
authors.initials: H
authors.lastname: Cao
authors.forename: Niall J
authors.initials: NJ
authors.lastname: English
authors.forename: J M D
authors.initials: JM
authors.lastname: MacElroy
mesh_terms: D004058:Diffusion; D005663:Furans / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry*; D056004:Molecular Dynamics Simulation; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D005663:Furans; D014867:Water; C018674:tetrahydrofuran; D006859:Hydrogen