Application of Synchrotron Radiation in the Study of the Structure and Dynamics of Amorphous Ices and Clathrate Hydrates

2004 ◽  
Author(s):  
John S. Tse
Keyword(s):  
Synchrotron Radiation ◽  
Clathrate Hydrates ◽  
Structure And Dynamics ◽  
Amorphous Ices

Transitions in pressure-amorphized clathrate hydrates akin to those of amorphous ices

2019 ◽  
Vol 151 (1) ◽  
pp. 014502 ◽  
Author(s):  
Ove Andersson ◽  
Paulo H. B. Brant Carvalho ◽  
Ying-Jui Hsu ◽  
Ulrich Häussermann
Keyword(s):  
Clathrate Hydrates ◽  
Amorphous Ices

scholarly journals Physical Properties of Frozen Volatiles–Their Relevance to the Study of Comet Nuclei

1989 ◽  
Vol 116 (1) ◽  
pp. 227-241
Author(s):  
J. Klinger
Keyword(s):  
Physical Properties ◽  
Gas Production ◽  
Clathrate Hydrates ◽  
Cometary Nuclei ◽  
Water Ice ◽  
Kinetics Of Formation ◽  
Amorphous Ices ◽  
Comet Nuclei ◽  
Heating Up ◽  
Kinetics Of

AbstractThe structural and thermodynamical properties of water ice and ice mixtures containing CO, CO2, CH4, and NH3 are thought to be important for the evolution of cometary nuclei. Based on recent laboratory studies performed by several groups, an overview is given of the properties of various ices condensed at low temperatures and of their evolution during heating up to a temperature of about 200 K, typical of the perihelion temperature of a comet such as P/Halley. It is shown that the porous surface of amorphous water ice plays an important role in the retention of other volatiles. The kinetics of formation and of decomposition of clathrate hydrates are discussed. The molecular hydrates formed by NH3 are briefly presented, and the possibility of their occurrence in comet nuclei is discussed. With special attention drawn to amorphous ices and clathrate hydrates, a qualitative discussion of the influence of the physical properties of various types of ices on the thermal behavior of comet nuclei and on gas production rates of comets is presented.

Molecular Perspectives on Structure and Dynamics in Clathrate Hydrates

1994 ◽  
Vol 715 (1 Natural Gas H) ◽  
pp. 161-176 ◽  
Author(s):  
JOHN A. RIPMEESTER ◽  
C. I. RATCLIFFE ◽  
D. D. KLUG ◽  
J. S. TSE
Keyword(s):  
Clathrate Hydrates ◽  
Structure And Dynamics

Structure and Dynamics of Propylene Oxide and Trimethylene Oxide Clathrate Hydrates

2004 ◽  
Vol 840 ◽  
Author(s):  
Inmaculada Peral ◽  
Joseph E. Curtis ◽  
Bryan C. Chakoumakos ◽  
Camille Y. Jones
Keyword(s):  
Neutron Scattering ◽  
Propylene Oxide ◽  
Neutron Powder Diffraction ◽  
Clathrate Hydrates ◽  
Cyclic Ethers ◽  
Structure And Dynamics ◽  
Trimethylene Oxide ◽  
Quasielastic Neutron ◽  
Quasielastic Neutron Scattering ◽  
Dynamics Simulations

ABSTRACTWe present results from studies of the structure and dynamics of clathrate hydrates of three cyclic ethers by neutron diffraction and preliminary results on molecular dynamics simulations. Recent results from neutron powder diffraction and quasielastic neutron scattering of studies of propylene oxide (PO, C3H6O) and its isomer trimethyelene oxide (TMO, C3H6O), are compared with structural results obtained previously for tetrahydrofuran (THF, C3H5O). Experimental evidence of distortions of the host structures with temperature is discussed in light of the findings from quasielastic neutron scattering, which indicate distinct regions of high-temperature and low-temperature rotational dynamics and a temperature dependence related to the size of the guest. Preliminary MD results indicate a general expansion of the lattice with temperature resulting in increased volume available to PO.

scholarly journals Type II Clathrate Hydrate Formation in Cometary Ice Analogs in Vacuo

1992 ◽  
Vol 150 ◽  
pp. 437-438
Author(s):  
D. F. Blake ◽  
L. Allamandola ◽  
S. Sandford ◽  
D. Hudgins ◽  
F. Freund
Keyword(s):  
High Vacuum ◽  
Hydrate Formation ◽  
Clathrate Hydrate ◽  
Clathrate Hydrates ◽  
Type Ii ◽  
State Transformation ◽  
Solid State Transformation ◽  
Guest Molecules ◽  
Amorphous Ices ◽  
Analog Experiments

Clathrate Hydrates can be formed under high vacuum conditions by annealing vapor-deposited amorphous ices of the appropriate composition. When astrophysically significant H2O:CH3OH ices are deposited and annealed, Type II Clathrate Hydrates are formed which can hold up to 6 mole % large guest molecules such as methanol and 12 mole % small guest molecules such as CO2 and CO. The solid state transformation of amorphous mixed molecular ice into crystalline clathrate hydrate and its sublimation at higher temperatures may serve to explain heretofore anomalous mechanical and gas release properties observed in cometary ices and laboratory ice analog experiments.

scholarly journals Current Status and Future Directions of Atomic Studies by Electron Spectrometry with Synchrotron Radiation

1986 ◽  
Vol 39 (5) ◽  
pp. 601 ◽  
Author(s):  
MO Krause
Keyword(s):  
Electronic Structure ◽  
Synchrotron Radiation ◽  
Recent Work ◽  
Current Status ◽  
Future Directions ◽  
Structure And Dynamics ◽  
New Directions ◽  
Electron Spectrometry

Representative examples of recent work on the electronic structure and dynamics of atoms are discussed and new directions in studies by electron spectrometry with synchrotron radiation (ESSR) are indicated.

Direct Observation of Monolayer Zones in Al-wt 4% Cu

1990 ◽  
Vol 48 (1) ◽  
pp. 14-15
Author(s):  
B. Jouffrey ◽  
D. Dorignac ◽  
A. Bourret
Keyword(s):  
Solid Solution ◽  
Synchrotron Radiation ◽  
Direct Observation ◽  
Supersaturated Solid Solution ◽  
Original Model ◽  
X Ray ◽  
Image Position

Since the early works on GP zones and the model independently proposed by Preston and Guinier on the first steps of precipitation in supersaturated solid solution of aluminium containing a few percent of copper, many works have been performed to understand the structure of different stages in the sequence of precipitation.The scheme which is generally admitted can be drawn from a work by Phillips.In their original model Guinier and Preston analysed a GP zone as composed of a single (100) copperrich plane surrounded by aluminum atomic planes with a slightly shorter distance from the original plane than in the solid solution.From X-ray measurements it has also been shown that GP1 zones were not only copper monolayer zones. They could be up to a few atomic planes thick. Different models were proposed by Guinier, Gerold, Toman. Using synchrotron radiation, proposals have been recently made.

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