scholarly journals Molecular Dynamics Study of Guest–Host Hydrogen Bonding in Ethylene Oxide, Trimethylene Oxide, and Formaldehyde Structure I Clathrate Hydrates

2017 ◽  
Vol 121 (16) ◽  
pp. 8832-8840 ◽  
Author(s):  
Hossein Mohammadi-Manesh ◽  
Hakime Ghafari ◽  
Saman Alavi
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonding ◽  
Ethylene Oxide ◽  
Clathrate Hydrates ◽  
Trimethylene Oxide

Far infrared absorption and rotational vibrations of the guest molecules in structure I clathrate hydrates between 4.3 and 100 K

1977 ◽  
Vol 55 (10) ◽  
pp. 1777-1785 ◽  
Author(s):  
John E. Bertie ◽  
Stephen M. Jacobs
Keyword(s):  
Ethylene Oxide ◽  
Guest Molecule ◽  
Signal To Noise Ratio ◽  
Michelson Interferometer ◽  
Far Infrared ◽  
Force Constants ◽  
Clathrate Hydrates ◽  
High Signal ◽  
Guest Molecules ◽  
Trimethylene Oxide

The infrared spectra between 330 and 15 cm−1 of the structure I clathrate hydrates of ethylene oxide, cyclopropane, and trimethylene oxide, at 4.3 K are presented. The spectra have an unusually high signal-to-noise ratio made possible by a Michelson interferometer and a silicon bolometer detector which operates at 1.2 K. Rotational vibrations of the guest molecules were observed at 65.0 and 35.6 cm−1 for ethylene oxide and at 69 and 50 cm−1 for trimethylene oxide. Inter-guest coupling of rotational vibrations is small and the two frequencies are assigned to vibrations about different inertial axes. The resulting force constants are 487 and 264 ferg rad−2 for ethylene oxide and 1190 and 1130 ferg rad−2 for trimethylene oxide and are discussed in relation to the barriers to reorientation of the guest molecule. The bands due to these vibrations are fairly sharp at 4.3 K, but are broad and poorly defined at 100 K. The guest and water vibrations interact predominantly through their transition dipoles, although the main contribution to the force constants of the rotational vibrations is from steric forces. The absorption by the water vibrations above 100 cm−1 is very similar for ethylene oxide and cyclopropane hydrates but significantly different for trimethylene oxide hydrate. Strong objections exist to the obvious interpretations of this difference which remains unexplained.

scholarly journals A molecular dynamics study of guest–host hydrogen bonding in alcohol clathrate hydrates

2015 ◽  
Vol 17 (19) ◽  
pp. 12639-12647 ◽  
Author(s):  
Masaki Hiratsuka ◽  
Ryo Ohmura ◽  
Amadeu K. Sum ◽  
Saman Alavi ◽  
Kenji Yasuoka
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonding ◽  
Molecular Dynamics Simulations ◽  
Vibrational Spectra ◽  
Clathrate Hydrates ◽  
Dynamics Simulations

Molecular dynamics simulations showed the significant impacts of the guest–host hydrogen bonding on the cage stability and vibrational spectra of the clathrate hydrates.

Effect of nitrogen atom substitution in cyclic guests on properties of structure H clathrate hydrates

2015 ◽  
Vol 93 (8) ◽  
pp. 906-912 ◽  
Author(s):  
Kazuki Imasato ◽  
Kotaro Murayama ◽  
Satoshi Takeya ◽  
Saman Alavi ◽  
Ryo Ohmura
Keyword(s):  
Molecular Dynamics ◽  
Hydrogen Bonding ◽  
Nitrogen Atom ◽  
Thermal Expansivity ◽  
Clathrate Hydrates ◽  
Dynamics Simulation ◽  
X Ray Diffraction ◽  
Large Cage ◽  
X Ray ◽  
Lattice Constants

The effect of substituting nitrogen heteroatoms in the cyclohexane ring of methylcyclohexane on the structure and guest dynamics of structure H (sH) clathrate hydrates with methane help gases are studied through experimental synthesis, powder X-ray diffraction (PXRD) measurements, and classical molecular dynamics simulation of methylcyclohexane and 1-methylpiperidine. The PXRD measurements were performed for temperatures in the range of 138 to 183 K, and the a axis and c axis lattice constants were determined in this temperature range. The PXRD results show the different thermal expansivity of lattice constants in both sH hydrate cages. Simulations on methylcyclohexane and 1-methylpiperidine are performed, and the effects of methane cage occupancy on the lattice constants were studied by simulations with 100% and 80% of the small and medium cages occupied by methane. The sH phases do not expand isotropically, and the a and c lattice constants can vary over a range of 0.015 Å and 0.06 Å, respectively, depending on the large cage guest and methane occupancy. Hydrogen bonding between the 1-methylpiperidine nitrogen atom and cage water in the sH hydrate are not observed in the simulations, and differences in behavior of the two sH hydrates are likely related to the differences in geometry of the large guests and occupancies of methane in the small and medium sH cages.

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