Infrared spectra from 300 to 10 cm−1 of structure II clathrate hydrates at 4.3 °K

Bertie, John E.; Jacobs, S. M.

doi:10.1063/1.437089

Cited by 49 publications

(20 citation statements)

References 33 publications

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“…In recent far-infrared spectroscopic measurements on phase a at low temperatures, Bertie and Jacobs (3) found that a principal absorption assigned to rotational vibrations of the THF molecules occurred at a wave number of about 25 cm-I. The corresponding energy, expressed in terms of temperature, is TRv = 36K.…”

Section: Phase Amentioning

confidence: 97%

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

Ross¹,

Andersson²

1982

Can. J. Chem.

108

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RUSSELL G. Ross and PER ANDERSSON. Can. J. Chem. 60,881 (1982). Solid phases in the tetrahydrofuran-water (THF-H20) system were investigated in the temperature range 100-260K and at pressures up to 1.5 GPa. Thermal conductivity, h, and heat capacity per unit volume, pc,, were measured, using the transient hot-wire method. We made measurements on solid phases having nominal compositions THF.17H20, THF,7.1H20, and THF.4.6H20, which we refer to as phases a , P, and y , respectively. Phase a is known to be a structure I1 clathrate hydrate, and h for this phase was found to be similarto other crystalline solids which areglass-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 a , were probably rotational vibrations of the THF guest molecules. Phase was similar, and we inferred that it was probably a structure I clathrate hydrate. Phase y behaved nearly like a normal crystal phase at low temperatures, but h became almost independent of temperature near melting. At 1.1 GPa and 130 K, we found evidence that phase a 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. RUSSELL G. ROSS et PER ANDERSSON. Can. J. Chem. 60, 881 (1982). On a ttudie les phases solides dans le systkme tetrahydrofuranne-eau (THF-H20) dans un intewalle de temperature allant de 100 a 260 K et des pressions allant jusqu'a 1,s GPa. On a mesure la conductivite thermique, h, et la capaciti calorifique par unite de volume, pc,, en utilisant la methode du fil chaud transitoire. Nous avons effectue ces mesures sur des phases solides ayant des compositions nominales de THF.17H20, THF.7,1H20 et THF4,6H20 que nous disignons respectivement comme phases a,p et y.On sait que la phase a a une structure I1 d'hydrate de clathrate et on a trouvt que, pour cette phase, h est semblable a celui d'autres solides cristallins qui ressemblent des verres si I'on tient compte de leurs proprietes thermiques. On sait que les excitations de faible energie sont relikes aux proprietes des solides ressemblant a des verres et, dans le cas de la phase a, ce sont probablement des vibrations-rotations des molecules-h8tes de THF. La phase P est semblable et nous en diduisons qu'elle a probablement une structure I d'hydrate de clathrate. La phase y se comporte presque comme une phase cristalline normale a basse temperature, mais h devient presqu'indtpendant de la temperature au voisinage du point de fusion. A 1,l GPa et 130 K, nous avons trouve des indications a l'effet que la phase a se transforme, sous pression, en une forme metastable qui peut &tre une nouvelle forme d'hydrate de clathrate a haute densite. Nous mentionnons brikvement les implications astrophysiques de nos resultats.[Traduit par le journal]

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Section: Phase Amentioning

confidence: 97%

“…A guest molecule may be considered to and on thermal properties of nonmetallic solids. undergo relatively free rotational vibrations within Structural disorder, and its effects, will be a its cage (3). recurring theme.…”

Section: Introductionmentioning

confidence: 99%

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

Ross¹,

Andersson²

1982

Can. J. Chem.

108

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“…35. Over longer (experimental) time scales, this e/m-response would be of interest to the macroscopic, experimental dielectric-response measurements of Bertie et al, 66,67 which established that water molecules rotate about half as rapidly as those in ice, even though the hydrogen bonds are similar in strength to those in ice. 68 Rick and Freeman 69 elucidated the proton-disorderpropagation mechanisms explaining this dielectric response, using hybrid Monte Carlo and MD, but this would not be possible with deterministic NEMD in the presence of e/m fields.…”

Section: Resultsmentioning

confidence: 97%

Global-density fluctuations in methane clathrate hydrates in externally applied electromagnetic fields

Waldron

English

2017

The Journal of Chemical Physics

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Non-equilibrium molecular-dynamics simulations of bulk methane clathrate hydrates have been conducted in a range of externally applied electromagnetic (e/m) fields. Studies into frequencies of system(or "global")-mass-density fluctuations showed that these clathrates have three major modes: the dominant one is attributable to water molecules' librations and occurs at 720 cm, regardless of any applied e/m fields. One of the more minor system-density fluctuations arises at 10-12 cm and is caused by the propagation of local-density fluctuations; again, this is independent of e/m fields. The final density fluctuation is caused by e/m fields, and it only becomes apparent for field strengths of 1.2 V/nm or higher. The frequency of this mode is always twice the frequency of the applied e/m field. It was shown that the main qualitative features of the translational and librational densities of states (DOSs) were unaffected by the application of e/m fields; however, a slight coupling effect was observed, producing a peak in all DOSs at the frequency of the applied field. This study showed that e/m fields below a certain intensity threshold do not lead to any marked structural distortion or dissociation effect on pre-existing bulk clathrates, in which the hydrogen-bonding structure of the lattice remains intact. This is verified by system-density and configurational-energy values as well as radial distribution functions.

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“…The limiting frequencies were chosen by trial and error to be 60 and 90 K. Once this fit was made for PPP, all other phenylenecontaining polymers could be treated without further corrections. 6 To summarize this section: The lowest frequency vibrations are best obtained from heat capacity measurements. The change from cubic to linear cumulative frequency spectra is well represented by tke Tarasov molecules with phenylene groups within a backbone chain cannot be fitted by a Tarasov function, but an easy correction is possible by adding two narrow, lower frequency modes of vibration.…”

Section: In Figures 2-4 a Comparison Between The Computed Integralmentioning

confidence: 99%

Study of skeletal vibrations used to compute heat capacities of solid macromolecules

Bu¹,

Cheng²,

Wunderlich³

1987

J. Phys. Chem.

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4179and ammonia draws the Cu2+ into the main channels to positions near the channel intersections.The Cuz+ forms complexes with two molecules of methanol, three of ethanol, three of pyridine, and four of ammonia. Nonpolar molecules such as ethylene are slower at effecting migration of the Cu2+. The lack of interaction between Cuz+ and o-xylene confirms that the exchanged Cu2+ is not on the external zeolite ulation from ESEM spectroscopy suggests that the Cu2+ is not directly associated with zeolitic aluminum. Acknowledgment.The limits of the application of the Tarasov approximation for the calculation of heat capacities of linear macromolecules are discussed by comparison with normal-mode analyses and by modification of the two-parameter equation. The discussion is based on data generated for about 70 macromolecules and some structure correlations are given for the characteristic temperatures. This work had led to a theory-based prediction scheme for heat capacities of linear macromolecules.

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Infrared spectra from 300 to 10 cm−1 of structure II clathrate hydrates at 4.3 °K

Cited by 49 publications

References 33 publications

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

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

Global-density fluctuations in methane clathrate hydrates in externally applied electromagnetic fields

Study of skeletal vibrations used to compute heat capacities of solid macromolecules

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