scholarly journals Über die Struktur und das Hochdruckverhalten des β-Li6UO6.

1976 ◽  
Vol 31 (8) ◽  
pp. 1053-1057 ◽  
Author(s):  
Jürgen Hauck ◽  
Matthias Rosenhauer
Keyword(s):  
Solid Solution ◽  
High Pressure ◽  
Phase Transformation ◽  
Low Temperature ◽  
Crystal Structures ◽  
Infrared Spectra ◽  
Invariant Point ◽  
Close Relationship ◽  
Triclinic Unit Cell ◽  
Reversible Phase

Li6UO6 has a reversible phase transformation at 680°C and decomposes above about 850°C. At high pressure the low temperature modification becomes unstable because of an invariant point in the system Li2O—Li4UO5 at approximately 13 Kb and 620°C. β-Li6UO6 has a triclinic unit cell with a = 5.203, b= 5.520, c = 5.536 Å, α = 114.7, β = 120.7 and γ = 75.5°. The close relationship between the crystal structures of Li6TeO6 and Li6UO6 is also suggested from similar infrared spectra and from partial solid solution Li6UO6—Li6TeO6.

Low Temperature (4K) and High Pressure (6.5 Kbars) Crystal Structures of (TMTSF)2PF6

1985 ◽  
Vol 119 (1) ◽  
pp. 225-232 ◽  
Author(s):  
Bernard Galiois ◽  
Jacques Gaultier ◽  
Christian Hauw ◽  
Daniel Chasseau ◽  
Alain Meresse ◽  
...  
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Crystal Structures

Low-Temperature Properties of High-Pressure Quenched f.c.c. Al-Si Solid Solution

1989 ◽  
Vol 8 (2) ◽  
pp. 173-178 ◽  
Author(s):  
J Chevrier ◽  
J. C Lasjaunias ◽  
F Zougmore ◽  
J. J Capponi
Keyword(s):  
Solid Solution ◽  
High Pressure ◽  
Low Temperature

Irreversible single-crystal to polycrystal and reversible single-crystal to single-crystal phase transformations in cyanurates

2001 ◽  
Vol 57 (6) ◽  
pp. 791-799 ◽  
Author(s):  
Menahem Kaftory ◽  
Mark Botoshansky ◽  
Moshe Kapon ◽  
Vitaly Shteiman
Keyword(s):  
Phase Transformation ◽  
High Temperature ◽  
Low Temperature ◽  
Single Crystal ◽  
High Temperature Phase ◽  
Monoclinic Space Group ◽  
Temperature Phase ◽  
Space Group ◽  
Reversible Phase ◽  
Low Temperature Phase

4,6-Dimethoxy-3-methyldihydrotriazine-2-one (1) undergoes a single-crystal to single-crystal reversible phase transformation at 319 K. The low-temperature phase crystallizes in monoclinic space group P21/n with two crystallographically independent molecules in the asymmetric unit. The high-temperature phase is obtained by heating a single crystal of the low-temperature phase. This phase is orthorhombic, space group Pnma, with the molecules occupying a crystallographic mirror plane. The enthalpy of the transformation is 1.34 kJ mol−1. The small energy difference between the two phases and the minimal atomic movement facilitate the single-crystal to single-crystal reversible phase transformation with no destruction of the crystal lattice. On further heating, the high-temperature phase undergoes methyl rearrangement in the solid state. 2,4,6-Trimethoxy-1,3,5-triazine (3), on the other hand, undergoes an irreversible phase transformation from single-crystal to polycrystalline material at 340 K with an enthalpy of 3.9 kJ mol−1; upon further heating it melts and methyl rearrangement takes place.

PHASE TRANSFORMATION OF BN NANOPARTICLES UNDER HIGH PRESSURE LOW TEMPERATURE CONDITIONS

2005 ◽  
Vol 19 (15n17) ◽  
pp. 2663-2668 ◽  
Author(s):  
Z. CHEN ◽  
Z. F. LAI ◽  
K. LI ◽  
D. L. CUI ◽  
N. LUN ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Low Temperature ◽  
Boron Nitride ◽  
Hot Pressing ◽  
Cubic Boron Nitride ◽  
Strong Interactions ◽  
Hot Press ◽  
Temperature Conditions ◽  
Pressing Time

Phase transformation of BN nanoparticles under high pressure (580~860MPa) and low temperature (270~325°C) hot press conditions was investigated. It was found that the contents of orthorhombic boron nitride (oBN) and cubic boron nitride (cBN) increased with the increase of temperature and the prolonging of hot pressing time under high pressure conditions. At the same time, because of the intergrowth of hBN, oBN and cBN. there are strong interactions among these three phases.

scholarly journals The high-pressure and low-temperature structural behaviour of 2,2,2-trifluoroethanol

CrystEngComm ◽  
2019 ◽  
Vol 21 (30) ◽  
pp. 4501-4506
Author(s):  
S. A. Barnett ◽  
D. R. Allan
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Crystal Structures ◽  
Structural Behaviour

Polymorphic crystal structures have been determined for 2,2,2-trifluoroethanol by using the in situ crystallography techniques of high pressure and cryo-cooling.

scholarly journals Reversible Phase Transformation in Y2O3 Under High Pressure

2009 ◽  
Vol 15 (S2) ◽  
pp. 1006-1007 ◽  
Author(s):  
JF Al-Sharab ◽  
BH Kear ◽  
OA Voronov ◽  
RK Sadangi ◽  
SL Deutsch ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transformation ◽  
Reversible Phase

Extended abstract of a paper presented at Microscopy and Microanalysis 2009 in Richmond, Virginia, USA, July 26 – July 30, 2009

Pressure-Induced Nano-Crystallization of Y2O3

2011 ◽  
Vol 1297 ◽  
Author(s):  
Stuart Deutsch ◽  
Jafar F. Al-Sharab ◽  
Bernard H. Kear ◽  
Stephen D. Tse
Keyword(s):  
Phase Transition ◽  
Grain Size ◽  
High Pressure ◽  
Phase Transformation ◽  
Monoclinic Phase ◽  
Transformation Process ◽  
Coarse Grained ◽  
Nanocrystalline State ◽  
Phase Transformation Process ◽  
Reversible Phase

ABSTRACTA reversible-phase transformation process to convert coarse-grained polycrystalline cubic-Y2O3 directly into the nanocrystalline state is being developed. The process involves a forward cubic-to-monoclinic phase transition under high pressure and a backward transformation from monoclinic-to-cubic under a lower pressure. The process has been used to reduce the grain size of fully dense cubic-Y2O3 from 300 μm to 0.1 μm. A surface modification effect, comprising a columnar-grained structure, has also been observed. Preliminary work indicates that the surface structure is modified, apparently formed by interaction between the graphite heater and sample.

Realizing Predicted Crystal Structures at Extreme Conditions:  The Low-Temperature and High-Pressure Crystal Structures of 2-Chlorophenol and 4-Fluorophenol

2005 ◽  
Vol 5 (3) ◽  
pp. 1055-1071 ◽  
Author(s):  
Iain D. H. Oswald ◽  
David R. Allan ◽  
Graeme M. Day ◽  
W. D. Samuel Motherwell ◽  
Simon Parsons
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Crystal Structures ◽  
Extreme Conditions

scholarly journals The low-temperature and high-pressure crystal structures of cyclobutanol (C4H7OH)

2005 ◽  
Vol 61 (4) ◽  
pp. 449-454 ◽  
Author(s):  
Pamela A. McGregor ◽  
David R. Allan ◽  
Simon Parsons ◽  
Colin R. Pulham
Keyword(s):  
High Pressure ◽  
Low Temperature ◽  
Crystal Structures ◽  
X Ray Diffraction ◽  
Structural Behaviour ◽  
Coordination Environment ◽  
X Ray ◽  
Alkyl Groups ◽  
Graph Set ◽  
Packing Arrangement

The low-temperature and high-pressure crystal structures of cyclobutanol (C4H7OH) have been determined using single-crystal X-ray diffraction techniques. At temperatures below 220 K, cyclobutanol crystallizes in the Aba2 space group (Z′ =  2) and its crystal structure is composed of pseudo-threefold hydrogen-bonded molecular catemers [assigned as C_2^2(4) in graph-set notation], which lie parallel to the crystallographic a axis. At a pressure of 1.3 GPa, the crystal symmetry changes to Pna21 (Z′  =  1) and the molecular catemers [expressed as C(2) in graph-set notation] adopt a pseudo-twofold arrangement. This structural behaviour is in agreement with our previous observations for phenol and its halogenated derivatives 2-chlorophenol and 4-fluorophenol, where pressure was found to favour a molecular packing more closely associated with small alkyl groups rather than that of relatively bulky alkyl groups. In addition, an examination of the molecular coordination environment in the low-temperature and high-pressure structures of cyclobutanol reveals that the change in structure on application of pressure appears to be driven by the molecules assuming a packing arrangement which more closely resembles that adopted in hard-sphere structures.

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