Phase transitions in ReO3studied by high-pressure X-ray diffraction

2000 ◽  
Vol 33 (2) ◽  
pp. 279-284 ◽  
Author(s):  
J.-E. Jørgensen ◽  
J. Staun Olsen ◽  
L. Gerward
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Powder Diffraction ◽  
Ambient Pressure ◽  
Rhombohedral Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Ions ◽  
Pressure Phase ◽  
Related Phase

ReO3has been studied at pressures up to 52 GPa by X-ray powder diffraction. The previously observed cubicIm3¯ high-pressure phase was shown to transform to a monoclinic MnF3-related phase at about 3 GPa. All patterns recorded above 12 GPa could be indexed on rhombohedral cells. The compressibility was observed to decrease abruptly at 38 GPa. It is therefore proposed that the oxygen ions are hexagonally close packed above this pressure, giving rise to two rhombohedral phases labelled I and II. The zero-pressure bulk moduliBoof the observed phases were determined and the rhombohedral phase II was found to have an extremely large value of 617 (10) GPa. It was found that ReO3transforms back to thePm3¯mphase found at ambient pressure.

High-Pressure Phase Transitions of Cubic Y 2 O 3 under High Pressures by In-situ Synchrotron X-Ray Diffraction

2019 ◽  
Vol 36 (4) ◽  
pp. 046103 ◽  
Author(s):  
Sheng Jiang ◽  
Jing Liu ◽  
Xiao-Dong Li ◽  
Yan-Chun Li ◽  
Shang-Ming He ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
High Pressures ◽  
High Pressure Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pressure Phase

High-pressure X-ray diffraction studies of potassium chlorate

2011 ◽  
Vol 45 (1) ◽  
pp. 48-52 ◽  
Author(s):  
Michael Pravica ◽  
Ligang Bai ◽  
Neelanjan Bhattacharya
Keyword(s):  
High Pressure ◽  
Decomposition Rate ◽  
Ambient Pressure ◽  
Rhombohedral Phase ◽  
Potassium Chlorate ◽  
X Ray Diffraction ◽  
X Ray ◽  
Induced Decomposition ◽  
Xrd Patterns ◽  
Pressure Regime

Two static high-pressure X-ray diffraction (XRD) studies of potassium chlorate have been performed at pressures of up to ∼14.3 GPa in a diamond anvil cell at ambient temperature using the 16 ID-B undulator beamline at the Advanced Photon Source for the X-ray source. The first experiment was conducted to ascertain decomposition rates of potassium chlorate as a function of pressure. Below 2 GPa, the sample was observed to decompose rapidly in the presence of the X-ray beam and release oxygen. Above 2 GPa (near the phase I → phase II transition), the decomposition rate dramatically slowed so that good quality XRD patterns could be acquired. This suggests a phase-dependent decomposition rate. In the second study, X-ray diffraction spectra were collected at pressures from 2 to 14.3 GPa by aligning virgin portions of the sample into the focused X-ray beam at each pressure. The results suggest the co-existence of mixed monoclinic (I) and rhombohedral (II) phases of potassium chlorate near 2 GPa. At pressures beyond 4 GPa, the XRD patterns show a very good fit to KClO3in the rhombohedral phase with space groupR3m, in agreement with earlier studies. No further phase transitions were observed with pressure. Decompression of the sample to ambient pressure indicated mixed phases I and II coupled with a small amount of synchrotron X-ray-induced decomposition product. The equation of state within this pressure regime has been determined.

scholarly journals Investigation of high-pressure planetary ices by cryo-recovery. II. High-pressure apparatus, examples and a new high-pressure phase of MgSO4·5H2O

2018 ◽  
Vol 51 (3) ◽  
pp. 692-705 ◽  
Author(s):  
Weiwei Wang ◽  
A. Dominic Fortes ◽  
David P. Dobson ◽  
Christopher M. Howard ◽  
John Bowles ◽  
...  
Keyword(s):  
High Pressure ◽  
Liquid Nitrogen ◽  
Powder Diffraction ◽  
Ambient Pressure ◽  
Ion Pairs ◽  
Phase Identification ◽  
Space Group ◽  
X Ray ◽  
Water Ice ◽  
Pressure Phase

An apparatus is described for the compression of samples to ∼2 GPa at temperatures from 80 to 300 K, rapid chilling to 80 K whilst under load and subsequent recovery into liquid nitrogen after the load is released. In this way, a variety of quenchable high-pressure phases of many materials may be preserved for examination outside the high-pressure sample environment, with the principal benefit being the ability to obtain high-resolution powder diffraction data for phase identification and structure solution. The use of this apparatus, in combination with a newly developed cold-loadable low-temperature stage for X-ray powder diffraction (the PheniX-FL), is illustrated using ice VI (a high-pressure polymorph of ordinary water ice that is thermodynamically stable only above ∼0.6 GPa) as an example. A second example using synthetic epsomite (MgSO4·7H2O) reveals that, at ∼1.6 GPa and 293 K, it undergoes incongruent melting to form MgSO4·5H2O plus brine, contributing to a long-standing debate on the nature of the high-pressure behaviour of this and similar highly hydrated materials. The crystal structure of this new high-pressure polymorph of MgSO4·5H2O has been determined at 85 K in space group Pna21 from the X-ray powder diffraction pattern of a sample recovered into liquid nitrogen and is found to differ from that of the known ambient-pressure phase of MgSO4·5H2O (pentahydrite, space group P {\overline 1}), consisting of corner-sharing MgO6–SO4 ion pairs rather than infinite corner-sharing chains.

High pressure phase transitions in organic solids II: X-ray diffraction study ofp-dichlorobenzene at high pressures

Pramana ◽  
1986 ◽  
Vol 27 (6) ◽  
pp. 835-839 ◽  
Author(s):  
Hema Sankaran ◽  
Surinder M Sharma ◽  
S K Sikka ◽  
R Chidambaram
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Diffraction Study ◽  
High Pressures ◽  
High Pressure Phase ◽  
X Ray Diffraction ◽  
Organic Solids ◽  
X Ray ◽  
Pressure Phase

scholarly journals Laser-Based Dynamic Compression of Solids to Ultrahigh Pressures

2014 ◽  
Vol 70 (a1) ◽  
pp. C396-C396
Author(s):  
Thomas Duffy ◽  
Jue Wang ◽  
Federica Coppari ◽  
Raymond Smith ◽  
Jon Eggert ◽  
...  
Keyword(s):  
High Pressure ◽  
Phase Transitions ◽  
Magnesium Oxide ◽  
Extrasolar Planets ◽  
Dynamic Compression ◽  
High Pressure Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pressure Phase ◽  
B2 Structure

Laser-based dynamic compression provides new opportunities to study the structures and properties of materials to ultrahigh pressure conditions. In this technique, high-powered laser beams are used to ablate a sample surface and by reaction a compression wave is generated and propagate through the sample. By controlling the shape and duration of the laser pulse, either shock or ramp (shockless) compression can be produced. Diagnostics include velocity interferometry (from which the stress-density response of the material can be determined) and x-ray diffraction from which structural information is obtained. Magnesium oxide is a fundamental ionic solid which has been extensively examined at high pressures. Theoretical studies predict a change in MgO from a rocksalt (B1) crystal structure to a cesium chloride (B2) structure at pressures of about 400–600 GPa but diamond anvil cell experiments have not been able to reach these pressures. Here we present dynamic X-ray diffraction measurements of ramp-compressed magnesium oxide. We show that a solid–solid phase transition, consistent with a transformation to the B2 structure occurs near 600 GPa. On further compression, this structure remains stable to 900 GPa. Our results provide an experimental benchmark to the equations of state and transition pressure of magnesium oxide, and may help constrain interior properties of super-Earth extrasolar planets. We have also examined the high-pressure behavior of molybdenum under both shock and ramp loading. The melting curves and high-pressure phase diagrams of transition metals have been controversial, and Mo is an excellent test case for resolving these discrepancies. We have conducted shock compression experiments on Mo with an X-ray diffraction diagnostic to address previous claims of high-pressure phase transitions and to determine the location of the Hugoniot melting point. We have also carried out ramp compression experiments to test predictions of phase transitions in Mo at ultrahigh pressures and low temperatures.

Pressure-induced polymorphism in phenol

2002 ◽  
Vol 58 (6) ◽  
pp. 1018-1024 ◽  
Author(s):  
David R. Allan ◽  
Stewart J. Clark ◽  
Alice Dawson ◽  
Pamela A. McGregor ◽  
Simon Parsons
Keyword(s):  
Crystal Structure ◽  
High Pressure ◽  
Ab Initio ◽  
Density Functional ◽  
Ambient Pressure ◽  
Energy Difference ◽  
X Ray Diffraction ◽  
X Ray ◽  
Pressure Melting ◽  
Pressure Phase

The high-pressure crystal structure of phenol (C6H5OH), including the positions of the H atoms, has been determined using a combination of single-crystal X-ray diffraction techniques and ab initio density-functional calculations. It is found that at a pressure of 0.16 GPa, which is just sufficient to cause crystallization of a sample held at a temperature just above its ambient-pressure melting point (313 K), a previously unobserved monoclinic structure with P21 symmetry is formed. The structure is characterized by the formation of hydrogen-bonded molecular chains, and the molecules within each chain adopt a coplanar arrangement so that they are ordered in an alternating 1-1-1 sequence. Although the crystal structure of the ambient-pressure P1121 phase is also characterized by the formation of molecular chains, the molecules adopt an approximate threefold arrangement. A series of ab initio calculations indicates that the rearrangement of the molecules from helical to coplanar results in an energy difference of only 0.162 eV molecule−1 (15.6 kJ mole−1) at 0.16 GPa. The calculations also indicate that there is a slight increase in the dipole moment of the molecules, but, as the high-pressure phase has longer hydrogen-bond distances, it is found that, on average, the hydrogen bonds in the ambient-pressure phase are stronger.

scholarly journals High-Pressure Structural Behavior and Equation of State of Kagome Staircase Compound, Ni3V2O8

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 910
Author(s):  
Daniel Diaz-Anichtchenko ◽  
Robin Turnbull ◽  
Enrico Bandiello ◽  
Simone Anzellini ◽  
Daniel Errandonea
Keyword(s):  
High Pressure ◽  
Equation Of State ◽  
Density Functional ◽  
Room Temperature ◽  
Ambient Pressure ◽  
Density Functional Theory Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Cell Parameters ◽  
A Chain

We report on high-pressure synchrotron X-ray diffraction measurements on Ni3V2O8 at room-temperature up to 23 GPa. According to this study, the ambient-pressure orthorhombic structure remains stable up to the highest pressure reached in the experiments. We have also obtained the pressure dependence of the unit-cell parameters, which reveals an anisotropic compression behavior. In addition, a room-temperature pressure–volume third-order Birch–Murnaghan equation of state has been obtained with parameters: V0 = 555.7(2) Å3, K0 = 139(3) GPa, and K0′ = 4.4(3). According to this result, Ni3V2O8 is the least compressible kagome-type vanadate. The changes of the crystal structure under compression have been related to the presence of a chain of edge-sharing NiO6 octahedral units forming kagome staircases interconnected by VO4 rigid tetrahedral units. The reported results are discussed in comparison with high-pressure X-ray diffraction results from isostructural Zn3V2O8 and density-functional theory calculations on several isostructural vanadates.

scholarly journals Neutron and high-pressure X-ray diffraction study of hydrogen-bonded ferroelectric rubidium hydrogen sulfate

2016 ◽  
Vol 72 (6) ◽  
pp. 855-863 ◽  
Author(s):  
Jack Binns ◽  
Garry J McIntyre ◽  
Simon Parsons
Keyword(s):  
High Pressure ◽  
Applied Pressure ◽  
Ferroelectric Material ◽  
Ferroelectric Materials ◽  
Hydrogen Sulfate ◽  
X Ray Diffraction ◽  
Temperature Dependent ◽  
X Ray ◽  
Pressure Phase ◽  
Hydrogen Bonded

The pressure- and temperature-dependent phase transitions in the ferroelectric material rubidium hydrogen sulfate (RbHSO4) are investigated by a combination of neutron Laue diffraction and high-pressure X-ray diffraction. The observation of disordered O-atom positions in the hydrogen sulfate anions is in agreement with previous spectroscopic measurements in the literature. Contrary to the mechanism observed in other hydrogen-bonded ferroelectric materials, H-atom positions are well defined and ordered in the paraelectric phase. Under applied pressure RbHSO4undergoes a ferroelectric transition before transforming to a third, high-pressure phase. The symmetry of this phase is revised to the centrosymmetric space groupP21/c, resulting in the suppression of ferroelectricity at high pressure.

Sign in / Sign up

Export Citation Format

Share Document