The binary intermetallic clathrates K8-xSi46 (x = 0.4; 1.2), Rb6.2Si46, Rb11.5Si136 and Cs7.8Si136 were prepared from M₄Si₄ (M = K, Rb, Cs) precursors by spark-plasma route (SPS) and structurally characterized by Rietveld refinement of PXRD data. The clathrate-II phase Rb11.5Si136 was synthesized for the first time. Partial crystallographic site occupancy of the alkali metals, particularly for ...

We report inelastic neutron scattering (INS) measurements on molecular hydrogen deuteride (HD) trapped in binary cubic (sII) and hexagonal (sH) clathrate hydrates, performed at low temperature using two different neutron spectrometers in order to probe both energy and momentum transfer. The INS spectra of binary clathrate samples exhibit a rich structure containing sharp bands arising from both...

Recently, for the first time a hydrate clathrate was discovered with hydrogen. Aside from the great technological promise that is inherent in storing hydrogen at high density at modest pressures, there is great scientific interest as this would constitute the first hydrate clathrate with multiple guest molecules per cage. The multiple cage occupancy is controversial, and reproducibility of the ...

One of the promising applications clathrate/gas hydrates is transport and storage natural gas. Semi-clathrate have received more attention due to milder pressure/temperature stability conditions compared ordinary clathrate hydrates. The most commonly reported semi-clathrate are formed from a combination gas + water quaternary ammonium salts. In this work, total 53 equilibrium data for methane T...

The 35C1 NQR frequencies o f A 2PdCl6 were studied. For A = (CH3)4N + a clathrate [(CH3)4N]2PdCl6 Cl2 was found and its crystal structure was determined (F d3c, Z = 32, a = 2554.5 pm, R = 0.062). The clathrate [(CH3)4N]2SnCl6 Cl2 was prepared, too. It is isomorphous with the corresponding palladium salt. The results o f the 35C1 NQR studies are discus­ sed on the basis o f the crystal structure.

Introduction: The likelihood that dissociating methane clathrate hydrate makes a significant contribution to martian atmospheric methane has been reported by [1-3]. The clathrate might be found in or beneath subsurface permafrost [1, 3-4], in surface ice such as glacial remnants [2], or, as reported here, in icy sediments. These reports suggest that triggers for clath-rate dissociation in recen...

Silicon clathrate compounds consist of fullerenelike polyhedral Si-cages, which share their faces to form a three-dimensional Si-sp 3 covalent network. Guest elements such as an alkali atom or an alkaliearth one can be encapsulated in the cage. Recently, these compounds have attracted strong interest due to the discovery of superconductivity in a metal-doped silicon clathrate, Ba6Na2Si46 [1], a...

Gas clathrate hydrates were first identified in 1810 by Sir Humphrey Davy. However, it is believed that other scientists, including Priestley, may have observed their existence before this date. They are solid crystalline inclusion compounds consisting of polyhedral water cavities which enclathrate small gas molecules. Natural gas hydrates are important industrially because the occurrence of th...

Gas mixtures of methane and ethane form structure II clathrate hydrates despite the fact that each of pure methane and pure ethane gases forms the structure I hydrate. Optimization of the interaction potential parameters for methane and ethane is attempted so as to reproduce the dissociation pressures of each simple hydrate containing either methane or ethane alone. An account for the structura...

Introduction: Clathrate hydrates are inclusion compounds, with an ice-like structure that consists in an arrangement of ice cages in which guest gas molecules are trapped individually. These structures are stabilized by van der Waals interactions between the gas and the cages [e.g. 1]. Their potential ubiquitous occurence in the Solar System [e.g. 2] has strong implications in various domains: ...