scholarly journals Cation Disorder Caused by Olivine-Ringwoodite Phase Transition Mechanism, Possible Explanation for Blue Olivine Inclusion in a Diamond

Minerals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 202
Author(s):  
William Bassett ◽  
Elise Skalwold
Keyword(s):  
Phase Transition ◽  
Natural Diamond ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transition Mechanism ◽  
Reducing Gas ◽  
Cation Disorder ◽  
Diamond Anvil ◽  
Soft Metal ◽  
Deep Focus

Synchrotron X-ray diffraction, as well as visual observations, in a diamond anvil cell (DAC) using soft metal gaskets or slightly reducing gas environment, have revealed that the olivine-ringwoodite transition in olivines of several compositions take place in two steps: step 1: displacive restacking of the oxygen layers, followed by step 2: diffusive reordering of the cations. The initiation of the phase transition was observed at temperatures as low as 200 °C below the reported temperature for the phase transition under hydrostatic conditions. These observations, especially residual disordered cations, have important implications for deep-focus earthquakes, the ability of ringwoodite to host surprising amounts of water, and possibly the observation of a blue olivine inclusion in a natural diamond from Brazil and in a pallasitic meteorite from Russia.

Effect of pressure on phase transitions in K1−xNaxMnF3(x = 0.04)

1999 ◽  
Vol 32 (2) ◽  
pp. 174-177 ◽  
Author(s):  
S. Åsbrink ◽  
A. Waśkowska ◽  
H. G. Krane ◽  
L. Gerward ◽  
J. Staun Olsen
Keyword(s):  
Phase Transition ◽  
Parent Compound ◽  
X Ray Diffraction ◽  
X Ray ◽  
Effect Of Pressure ◽  
Cell Dimensions ◽  
Main Effect ◽  
Diamond Anvil ◽  
Na Ions ◽  
Unit Cell Dimensions

The pressure-induced phase transition sequence in the title compound, potassium sodium fluoromanganate, has been investigated by single-crystal X-ray diffraction using synchrotron radiation and a diamond anvil pressure cell. Na^+ ions at 4% of the K^+ sites shift the ferrodistortive phase transition to the lower pressure P_{c1} of 2.75 (5) GPa compared to 3.12 GPa in the parent compound KMnF3. The transition is illustrated by the critical behaviour of the unit-cell dimensions, the pressure-dependent evolution of the MnF_6 ^- octahedral rotation and related macroscopic spontaneous strain. As far as precision of the present experiment allows, the observations show that the 4% of Na^+ admixture at the K^+ sites does not substantially change the nature of the transition at P_{c1}. The main effect of pressure is to stabilize the tetragonal phase II. The expected further evolution of the MnF_6 ^- octahedral tiltings, leading to the orthorhombic and monoclinic phases, has not been observed up to 8.33 GPa.

scholarly journals Structural Study of δ-AlOOH Up to 29 GPa

Minerals ◽  
2020 ◽  
Vol 10 (12) ◽  
pp. 1055
Author(s):  
Dariia Simonova ◽  
Elena Bykova ◽  
Maxim Bykov ◽  
Takaaki Kawazoe ◽  
Arkadiy Simonov ◽  
...  
Keyword(s):  
Phase Transition ◽  
Synchrotron Radiation ◽  
Equation Of State ◽  
Room Temperature ◽  
Diamond Anvil Cell ◽  
Volume Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diamond Anvil ◽  
Murnaghan Equation

A structure and equation of the state of δ-AlOOH has been studied at room temperature, up to 29.35 GPa, by means of single crystal X-ray diffraction in a diamond anvil cell using synchrotron radiation. Above ~10 GPa, we observed a phase transition with symmetry changes from P21nm to Pnnm. Pressure-volume data were fitted with the second order Birch-Murnaghan equation of state and showed that, at the phase transition, the bulk modulus (K0) of the calculated wrt 0 pressure increases from 142(5) to 216(5) GPa.

Crystal structure and the equation of state of thorium monophosphide for pressures up to 50 GPa

1989 ◽  
Vol 22 (1) ◽  
pp. 61-63 ◽  
Author(s):  
J. S. Olsen ◽  
L. Gerward ◽  
U. Benedict ◽  
H. Luo ◽  
O. Vogt
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
High Pressure ◽  
Synchrotron Radiation ◽  
Diamond Anvil Cell ◽  
X Ray Diffraction ◽  
Pressure Derivative ◽  
X Ray ◽  
Cscl Structure ◽  
Diamond Anvil

High-pressure X-ray diffraction studies have been performed on ThP using synchrotron radiation and a diamond-anvil cell. The bulk modulus B 0 and its pressure derivative B′0 have been determined (B 0 = 137 GPa; B′0 = 5.1). A phase transition from the NaCl structure to the CsCl structure was observed at about 30 GPa.

Deep Earth mineralogy revealed by ultrahigh-pressure experiments

2014 ◽  
Vol 78 (2) ◽  
pp. 437-446 ◽  
Author(s):  
Kei Hirose
Keyword(s):  
Phase Transition ◽  
Ultrahigh Pressure ◽  
X Ray Diffraction ◽  
X Ray ◽  
Deep Earth ◽  
Diamond Anvil ◽  
Lowermost Part ◽  
Fe Alloys ◽  
Laser Heated

AbstractUltrahigh-pressure and -temperature (P-T) experimental techniques have progressed rapidly in recent years. By combining them with X-ray diffraction measurements at synchrotron radiation facilities, it is now possible to examine deep Earth mineralogy in situ at relevant high P-T conditions in a laser-heated diamond anvil cell (DAC). The lowermost part of the mantle, known as the D″ layer, has long been enigmatic because of a number of unexplained seismological features. Nevertheless, the discovery of a phase transition from MgSiO3 perovskite to ‘post-perovskite’ above 120 GPa and 2400 K indicates that post-perovskite is a principal constituent in the lowermost mantle, which is compatible with seismic observations. The ultrahigh P-T conditions of the Earth’s core have not been accessible by static experiments, but the structure and phase transition of Fe and Fe-alloys are now being examined up to 400 GPa and 6000 K by laser-heated DAC studies.

Study of Molecular Dynamics and the Solid State Phase Transition Mechanism for Unsymmetrical Thiopyrophosphate Using X-ray Diffraction, DFT Calculations and NMR Spectroscopy

2006 ◽  
Vol 110 (2) ◽  
pp. 761-771 ◽  
Author(s):  
Marek J. Potrzebowski ◽  
Grzegorz D. Bujacz ◽  
Anna Bujacz ◽  
Sebastian Olejniczak ◽  
Paweł Napora ◽  
...  
Keyword(s):  
Phase Transition ◽  
Molecular Dynamics ◽  
Solid State ◽  
Nmr Spectroscopy ◽  
Dft Calculations ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transition Mechanism

High-Pressure X-Ray Diffraction Studies of Elastic Anomalies in Superlattice

1991 ◽  
Vol 231 ◽  
Author(s):  
Y. Fujii ◽  
Y. Ohishi ◽  
H. Konishi ◽  
N. Nakayama ◽  
T. Shinjo
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Diamond Anvil Cell ◽  
Orthorhombic Phase ◽  
X Ray Diffraction ◽  
X Ray ◽  
Layer Stacking ◽  
Diamond Anvil ◽  
Elastic Anomalies ◽  
Structural Aspects

AbstractThis paper has made an overview on elastic and structural aspects of three distinct superlattices under hydrostatic pressure up to about 8GPa, which were studied by our unique x-ray diffraction technique incorporated with a diamond-anvil cell. They are metallic fcc/fcc Au/Ni, bcc/fcc Mo/Ni, and semiconductive epitaxially-grown PbSe/SnSe superlattices. In their layer-stacking direction, both metallic superlattices show the supermodulus behavior while the semiconductive one doesn't. However, its pressure-driven cubic-to-orthorhombic phase transition, successively taking place in the SnSe and PbSe layers, has been found to significantly shift by stress due to its epitaxial growth.

High Pressure Synchrotron Diffraction of KCa2Nb3O10, a Layered Perovskite Compound

1998 ◽  
Vol 524 ◽  
Author(s):  
K. A. Steiner ◽  
W. T. Petuskey
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Diamond Anvil Cell ◽  
Orthorhombic Phase ◽  
Layered Perovskite ◽  
X Ray Diffraction ◽  
Synchrotron Diffraction ◽  
X Ray ◽  
Lattice Constants ◽  
Diamond Anvil

ABSTRACTHigh pressure synchrotron x-ray diffraction experiments were conducted on KCa2Nb3O10, to determine lattice constants as a function of pressure. A diamond anvil cell was used to produce pressures up to 66 GPa. A phase transition occurred at 13.5 GPa. From the lattice constants, linear compressibilities of 8.55 × 10-4 GPa-1 in the a direction, -9.40 × 10-4 GPa-1 in the b direction, and 142 × 10-4 GPa-1 in the c direction, and a bulk modulus of 68.5 GPa were found for the lower pressure orthorhombic phase.

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