[1] Buffett and Archer (2004) showed a model of the steady state global ocean clathrate reservoir that reproduces drill data and predicts a global methane inventory of about 5000 Gton C. The model inventory is very sensitive to ocean temperature, with factor-of-two changes in methane inventory in response to temperature changes of 1.5 C. Here we explore the potential time-dependent behavior of ...

We use a statistical thermodynamic approach to determine the composition of clathrate hydrates which may form from a multiple compound gas whose composition is similar to that of Titan’s atmosphere. Assuming that noble gases are initially present in this gas phase, we calculate the ratios of xenon, krypton and argon to species trapped in clathrate hydrates. We find that these ratios calculated ...

We use an order-parameter formulation, in conjunction with non-Boltzmann sampling to study the nucleation of clathrate hydrates from water–CO2 mixtures, using computer simulations. A set of order parameters are defined: F i gg ~i51,2,...,n and gg for guest–guest!, which characterize the spatial and orientational order of the CO2 molecules, and F i hh ~hh for host–host!, which govern the orderin...

The cage occupancy of hydrogen clathrate hydrate has been examined by grand canonical Monte Carlo (GCMC) simulations for wide ranges of temperature and pressure. The simulations are carried out with a fixed number of water molecules and a fixed chemical potential of the guest species so that hydrogen molecules can be created or annihilated in the clathrate. Two types of the GCMC simulations are...

A series of alkali metal containing compounds with type I clathrate structure, A8Ga8Si38 (A = K, Rb, Cs) and K8Al8Si38, were synthesized and characterized. Room temperature lattice parameters of A8Ga8Si38 (A = K, Rb, Cs) and K8Al8Si38 were determined to be 10.424916(10), 10.470174(13), 10.535069(15), and 10.48071(2) Å, respectively. The type I clathrate structure (cubic, Pm3 ̅n) was confirmed fo...

Clathrate hydrates are crystalline compounds composed of hydrogen-bonded water molecules that form polyhedral cavities and trap small guest molecules such as methane, carbon dioxide, cyclopentane (CP), and tetrahydrofuran (THF). Understanding the formation and dissociation of clathrate hydrates is of significant importance to addressing some global challenges such as greenhouse gas mitigation a...

At low temperature (T) and high pressure (P), gas molecules can be held in ice cages to form crystalline molecular compounds that may have application for energy storage. We synthesized a hydrogen clathrate hydrate, H(2)(H(2)O)(2), that holds 50 g/liter hydrogen by volume or 5.3 wt %. The clathrate, synthesized at 200-300 MPa and 240-249 K, can be preserved to ambient P at 77 K. The stored hydr...

Four-wave mixing measurements are carried out on I(2)-doped ice, prepared by quench condensing the premixed vapor at 128 K. Coherent vibrational dynamics is observed in two distinct ensembles. The first is ascribed to trapping in asymmetric polar cages in which, as in water, the valence absorption of the molecule is blueshifted by 3500 cm(-1), predissociation of the B state is complete upon the...

The high pressure properties of the novel tetrel-free clathrate, Ba₈Cu13.1Zn3.3P29.6, were investigated using synchrotron powder X-ray diffraction. The pressure was applied using a diamond anvil cell. No structural transitions or decomposition were detected in the studied pressure range of 0.1-7 GPa. The calculated bulk modulus for Ba₈Cu13.1Zn3.3P29.6 using a third-order Birch-Murnaghan equatio...