scholarly journals Does cage quantum delocalisation influence the translation–rotational bound states of molecular hydrogen in clathrate hydrate?

2018 ◽  
Vol 212 ◽  
pp. 533-546 ◽  
Author(s):  
David M. Benoit ◽  
David Lauvergnat ◽  
Yohann Scribano
Keyword(s):  
Molecular Hydrogen ◽  
Bound States ◽  
Clathrate Hydrate ◽  
Guest Molecules

In this study, we examine the effect of a flexible description of the clathrate hydrate framework on the translation–rotation (TR) eigenstates of guest molecules such as molecular hydrogen.

Clathrate and other solid phases in the tetrahydrofuran–water system: thermal conductivity and heat capacity under pressure

1982 ◽  
Vol 60 (7) ◽  
pp. 881-892 ◽  
Author(s):  
Russell G. Ross ◽  
Per Andersson
Keyword(s):  
Thermal Conductivity ◽  
Heat Capacity ◽  
Water System ◽  
Clathrate Hydrate ◽  
Transient Hot Wire ◽  
Guest Molecules ◽  
Hydrate Phase ◽  
Wire Method ◽  
Solid Phases ◽  
Thermal Conductivity Λ

Solid phases in the tetrahydrofuran–water (THF–H2O) system were investigated in the temperature range 100–260 K and at pressures up to 1.5 GPa. Thermal conductivity, λ, and heat capacity per unit volume, ρcp, were measured, using the transient hot-wire method. We made measurements on solid phases having nominal compositions THF•17H2O, THF•7•1H2O, and THF•4•6H2O, which we refer to as phases α, β, and γ, respectively. Phase α is known to be a structure II clathrate hydrate, and λ for this phase was found to be similar to other crystalline solids which are glass-like in relation to their thermal properties. Low-energy excitations are known to be relevant to the properties of glass-like solids, and, in the case of phase α, were probably rotational vibrations of the THF guest molecules. Phase β was similar, and we inferred that it was probably a structure I clathrate hydrate. Phase γ behaved nearly like a normal crystal phase at low temperatures, but λ became almost independent of temperature near melting. At 1.1 GPa and 130 K, we found evidence that phase α transformed, on pressurization, to a metastable modification which may be a new high-density form of clathrate hydrate. The astrophysical implications of our results were mentioned briefly.

Comments on the Infrared Spectra of SO2 Clathrate-hydrate Formed by Vapor Condensation

1971 ◽  
Vol 49 (24) ◽  
pp. 4114-4115 ◽  
Author(s):  
A. H. Hardin ◽  
K. B. Harvey
Keyword(s):  
Amorphous Phase ◽  
Infrared Spectra ◽  
Transformation Temperature ◽  
Vapor Condensation ◽  
Clathrate Hydrate ◽  
Hindered Rotation ◽  
Guest Molecules ◽  
Gaseous Mixtures

Gaseous mixtures having clathrate-hydrate stoichiometries were condensed at 83 °K into an amorphous phase. Infrared spectra were recorded at a series of temperatures up to 180 °K in order to determine the transformation temperature and the nature of the annealed phase. Bands associated with the H2O molecules began to shift position at 125 °K while those attributed to guest molecules decreased to null intensity. There was no evidence of a unique clathrate-hydrate H2O spectrum nor of free or hindered rotation of the guest molecules.

Observation of Electric-Field-Induced Liberation of Guest Molecules from Clathrate Hydrate

2021 ◽  
pp. 10410-10416
Author(s):  
Ziyue Li ◽  
Mengjie Lyu ◽  
Hannes Jónsson ◽  
Christoph Rose-Petruck
Keyword(s):  
Electric Field ◽  
Clathrate Hydrate ◽  
Guest Molecules

Structural Transition of Trimethylamine Hydrate by Methane or Hydrogen Inclusion

2020 ◽  
Author(s):  
Minjun Cha
Keyword(s):  
Structural Transition ◽  
Guest Molecule ◽  
Clathrate Hydrate ◽  
Hydrogen Gas ◽  
Time Dependent ◽  
X Ray Diffraction ◽  
Guest Molecules ◽  
X Ray ◽  
Inclusion Process ◽  
Diffraction Patterns

<p>Recently, several alkylamine hydrates have been studied in an effort to reveal the structural transitions from semi- to ‘canonical’ clathrate hydrate in the presence of secondary guest molecules. Trimethylamine (TMA) is known to form the semi-clathrate hydrate, and it has been reported that the structural transition of the TMA semi-clathrate hydrate may not occur in the presence of hydrogen gas as a secondary guest molecule. This paper reports the structural transition of trimethylamine(TMA) hydrate induced by the type of guest molecules. Powder X-ray diffraction patterns of (TMA + H<sub>2</sub>) hydrates show the formation of hexagoanl P6/mmm hydrate, but those of (TMA + CH<sub>4</sub>) hydrates indicate the formation of cubic Fd3m hydrate. Without gaseous guest molecule, the crystal structure of pure TMA hydrate is identified as hexagonal P6/mmm. Therefore, inclusion of gaseous methane in TMA hydrate can induce the structural transition from hexagonal to cubic hydrate or the formation of metastable cubic hydrate. To clearly reveal this possibility, we also check the time-dependent structural patterns of binary (TMA + CH<sub>4</sub>) hydrates from 1 to 14 days, and the results show that the structural transition of TMA hydrate from hexagonal P6/mmm to cubic Fd3m hydrate structure can occur during the methane inclusion process.</p>

Dynamic Behavior of Diatomic Guest Molecules in Clathrate Hydrate Structure II

1997 ◽  
Vol 101 (32) ◽  
pp. 6290-6292 ◽  
Author(s):  
Shinichiro Horikawa ◽  
Hidenosuke Itoh ◽  
Jiro Tabata ◽  
Katsuyuki Kawamura ◽  
Takeo Hondoh
Keyword(s):  
Dynamic Behavior ◽  
Clathrate Hydrate ◽  
Guest Molecules

scholarly journals Nature of the Bound States of Molecular Hydrogen in Carbon Nanohorns

2007 ◽  
Vol 98 (21) ◽  
Author(s):  
F. Fernandez-Alonso ◽  
F. J. Bermejo ◽  
C. Cabrillo ◽  
R. O. Loutfy ◽  
V. Leon ◽  
...  
Keyword(s):  
Molecular Hydrogen ◽  
Bound States ◽  
Carbon Nanohorns

The Rotational Oscillations of Tetrahydrofuran in Tetrahydrofuran Clathrate Hydrate

1973 ◽  
Vol 51 (24) ◽  
pp. 4062-4071 ◽  
Author(s):  
D. D. Klug ◽  
E. Whalley
Keyword(s):  
Gas Phase ◽  
Low Frequency ◽  
Clathrate Hydrate ◽  
Water Molecules ◽  
Dielectric Measurements ◽  
Effective Dipole Moment ◽  
Orientational Disorder ◽  
Guest Molecules ◽  
Rotational Oscillations ◽  
Good Agreement

The absorptivity of tetrahydrofuran clathrate hydrate in the range 70–7 cm−1 has been measured at several temperatures in the range 17–80 K. There are two broad bands with maxima at 25 and 38 cm−1 which are due to the rotational oscillations of tetrahydrofuran molecules in their cages. The integrated absorptivity yields an effective dipole moment for the oscillation of 1.63 D, which is close to the gas-phase value. The negative second moment of the absorptivity yields the contribution 0.105 ± ~0.007 to the low-frequency refractive index, in good agreement with a less accurate value from dielectric measurements. The orientational disorder of the water molecules causes a distribution of potentials hindering the rotational oscillations of the guest molecules, and a detailed analysis of the shapes of the bands yields directly the distribution of force constants for the oscillations.

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