scholarly journals Synthesis and Compressibility of Novel Nickel Carbide at Pressures of Earth’s Outer Core

Minerals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 516
Author(s):  
Timofey Fedotenko ◽  
Saiana Khandarkhaeva ◽  
Leonid Dubrovinsky ◽  
Konstantin Glazyrin ◽  
Pavel Sedmak ◽  
...  
Keyword(s):  
Equation Of State ◽  
Outer Core ◽  
Direct Reaction ◽  
Volume Data ◽  
X Ray Diffraction ◽  
Nickel Carbide ◽  
Diamond Anvils ◽  
Group A ◽  
Diamond Anvil ◽  
Murnaghan Equation

We report the high-pressure synthesis and the equation of state (EOS) of a novel nickel carbide (Ni3C). It was synthesized in a diamond anvil cell at 184(5) GPa through a direct reaction of a nickel powder with carbon from the diamond anvils upon heating at 3500 (200) K. Ni3C has the cementite-type structure (Pnma space group, a = 4.519(2) Å, b = 5.801(2) Å, c = 4.009(3) Å), which was solved and refined based on in-situ synchrotron single-crystal X-ray diffraction. The pressure-volume data of Ni3C was obtained on decompression at room temperature and fitted to the 3rd order Burch-Murnaghan equation of state with the following parameters: V0 = 147.7(8) Å3, K0 = 157(10) GPa, and K0' = 7.8(6). Our results contribute to the understanding of the phase composition and properties of Earth’s outer core.

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.

scholarly journals Equation of State of a Natural Chromian Spinel at Ambient Temperature

Minerals ◽  
2018 ◽  
Vol 8 (12) ◽  
pp. 591 ◽  
Author(s):  
Zhongying Mi ◽  
Weiguang Shi ◽  
Lifei Zhang ◽  
Sean Shieh ◽  
Xi Liu
Keyword(s):  
Equation Of State ◽  
Simple Algorithm ◽  
Experimental Result ◽  
Chromian Spinel ◽  
Chemical Compositions ◽  
Volume Data ◽  
X Ray Diffraction ◽  
Pressure Derivative ◽  
Diamond Anvil ◽  
Murnaghan Equation

A natural chromian spinel with the composition (Mg0.48(3)Fe0.52(3))(Fe0.06(1)Al0.28(1)Cr0.66(2))2O4 was investigated up to 15 GPa via synchrotron X-ray diffraction with a diamond-anvil cell at room temperature. No phase transition was clearly observed up to the maximum experimental pressure. The pressure–volume data fitted to the third-order Birch–Murnaghan equation of state yielded an isothermal bulk modulus ( K T 0 ) of 207(5) GPa and its first pressure derivative ( K T 0 ′ ) of 3.2(7), or K T 0 = 202(2) GPa with K T 0 ′ fixed as 4. With this new experimental result and the results on some natural chromian spinels in the literature, a simple algorithm describing the relation between the K T 0 and the compositions of the natural chromian spinels was proposed. To examine this algorithm further, more compression experiments should be performed on natural chromian spinels with different chemical compositions.

Equation of state of hercynite, FeAl2O4, and high-pressure systematics of Mg-Fe-Cr-Al spinels

2015 ◽  
Vol 79 (2) ◽  
pp. 285-294 ◽  
Author(s):  
F. Nestola ◽  
B. Periotto ◽  
C. Anzolini ◽  
G. B. Andreozzi ◽  
A. B. Woodland ◽  
...  
Keyword(s):  
Equation Of State ◽  
Experimental Approach ◽  
Volume Data ◽  
X Ray Diffraction ◽  
Third Order ◽  
X Ray ◽  
Volume Equation ◽  
Overlap Method ◽  
Pulse Echo ◽  
Murnaghan Equation

AbstractIn this work a single crystal of synthetic hercynite, FeAl2O4, was investigated by X-ray diffraction up to 7.5 GPa and at room temperature, in order to determine its pressure–volume equation of state. The unit-cell volume decreases non-linearly with a reduction of 3.4% (i.e. 18.43 Å3). The pressure–volume data were fitted to a third-order Birch-Murnaghan equation of state providing the following coefficients: V0 = 542.58(3)Å3, KT0 = 193.9(1.7) GPa, K' = 6.0(5). These results are consistent with previous investigations of Cr and Al spinels measured with the same experimental approach but the KT0 differs significantly from the experimental determination carried out more than 40 years ago by Wang and Simmons (1972) by the pulse echo overlap method. Our new results were used to redetermine the FeAl2O4(hercynite) = FeO(wüstite) + Al2O3(corundum) equilibrium in P–T space and obtain geobarometric information for Cr-Al spinels found as inclusions in diamond.

scholarly journals The equation of state of thePmmnphase of NiSi

2015 ◽  
Vol 48 (6) ◽  
pp. 1914-1920 ◽  
Author(s):  
Oliver T. Lord ◽  
Andrew R. Thomson ◽  
Elizabeth T. H. Wann ◽  
Ian G. Wood ◽  
David P. Dobson ◽  
...  
Keyword(s):  
Equation Of State ◽  
Orthorhombic Phase ◽  
X Ray Diffraction ◽  
Third Order ◽  
X Ray ◽  
Pressure Medium ◽  
Diamond Anvil ◽  
Pressure Standard ◽  
Murnaghan Equation ◽  
Made In

The equation of state of the orthorhombic phase of NiSi withPmmnsymmetry has been determined at room temperature from synchrotron-based X-ray diffraction measurements of its lattice parameters, made in a diamond anvil cell. Measurements were performed up to 44 GPa, using Ne as the pressure medium and Au as the pressure standard. The resulting pressure–volume (P–V) data have been fitted with a Birch–Murnaghan equation of state of third order to yieldV0= 11.650 (7) Å3 atom−1,K0= 162 (3) GPa andK0′ = 4.6 (2). In addition,P–Vdata have been collected on Ni53Si47in the B20 structure using both Ne and He as the pressure media and Cu and Au as the pressure standards, also to 44 GPa. A fit using the same Birch–Murnaghan equation of state of third order yieldsV0= 11.364 (6) Å3 atom−1,K0= 171 (4) GPa andK0′ = 5.5 (3).

New pressure-induced phase transition to Co2Si-type Fe2P

2020 ◽  
Vol 105 (11) ◽  
pp. 1752-1755
Author(s):  
Yoichi Nakajima ◽  
Shunya Araki ◽  
Daisuke Kinoshita ◽  
Kei Hirose ◽  
Shigehiko Tateno ◽  
...  
Keyword(s):  
Phase Transition ◽  
Inner Core ◽  
Outer Core ◽  
Volume Data ◽  
X Ray Diffraction ◽  
Orthorhombic Unit Cell ◽  
Earth’S Inner Core ◽  
Murnaghan Equation ◽  
New Phase

Abstract We found a new phase transition in Fe2P from Co2P-type (C23) to Co2Si-type (C37) structure above 42 ± 2 GPa based on in situ X-ray diffraction experiments. While these two structures have identical crystallographic symmetry, the orthorhombic unit cell is shortened in a-axis but elongated in c-axis, the coordination number of phosphorous increases from nine to 10, and the volume reduces by 2% across the phase transition. The new C37-type Fe2P phase has been found to be stable, at least to 83 GPa at high temperature. The Birch-Murnaghan equation of state for C37 Fe2P was also obtained from pressure-volume data, suggesting that phosphorous contributes to 17% of the observed density deficit of the Earth's outer core when it includes the maximum 1.8 wt% P as observed in iron meteorites. In addition, since both Fe2S and Ni2Si are also known to have the C37 structure under high pressure, (Fe,Ni)2(S,Si,P) could have wide solid solution and constitute planetary iron cores, although it is not dense enough to be a main constituent of the Earth's inner core.

scholarly journals Quasi-hydrostatic equation of state of silicon up to 1 megabar at ambient temperature

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Simone Anzellini ◽  
Michael T. Wharmby ◽  
Francesca Miozzi ◽  
Annette Kleppe ◽  
Dominik Daisenberger ◽  
...  
Keyword(s):  
Equation Of State ◽  
Room Temperature ◽  
Uniaxial Stress ◽  
Sample Volume ◽  
X Ray Diffraction ◽  
Experimental Conditions ◽  
X Ray ◽  
Pressure Medium ◽  
Diamond Anvil ◽  
Isothermal Equation

Abstract The isothermal equation of state of silicon has been determined by synchrotron x-ray diffraction experiments up to 105.2 GPa at room temperature using diamond anvil cells. A He-pressure medium was used to minimize the effect of uniaxial stress on the sample volume and ruby, gold and tungsten pressure gauges were used. Seven different phases of silicon have been observed along the experimental conditions covered in the present study.

The deformation mechanism of a pressure-induced phase transition in dehydrated analcime

2012 ◽  
Vol 76 (1) ◽  
pp. 129-142 ◽  
Author(s):  
A. Yu. Likhacheva ◽  
S. V. Rashchenko ◽  
Yu. V. Seryotkin
Keyword(s):  
Phase Transition ◽  
Equation Of State ◽  
Structure Type ◽  
Elastic Behaviour ◽  
Structural Behaviour ◽  
Synchrotron Powder Diffraction ◽  
First Order Phase Transition ◽  
Diamond Anvil ◽  
First Order Phase ◽  
Murnaghan Equation

AbstractThe elastic and structural behaviour of dehydrated analcime in compression in a non-penetrating medium up to 3 GPa was studied in a diamond anvil cell using in situ synchrotron powder diffraction. A first-order phase transition at 0.4–0.7 GPa is accompanied by a symmetry change from monoclinic (I2/a) to pseudo-rhombohedral (R3) due to trigonalization of the aluminosilicate framework. This is due to the migration of cations to new positions close to the 6-membered rings forming the channels. The reduction of the mean aperture of the structure-forming 6- and 8-membered rings, as a result of tetrahedral tilting, leads to a 7.5% reduction in volume at the phase transition. The bulk modulus values are 38(2) GPa for the low pressure (LP) phase [fitted with a Murnaghan equation of state, K' = 4 (fixed)] and 11(4) GPa for the high pressure (HP) phase [fitted with a third-order Birch–Murnaghan equation of state, K' = 9(1)]. The elastic behaviour of the LP phase is anisotropic, with compressibilities βa:βb:βc in the ratio 1:4:2; the most compressible direction b coinciding with the orientation of empty 8-membered rings. The compressibility of the HP phase is isotropic. Trigonalization appears to be the most effective (and probably unique) mechanism of radical volume contraction for the ANA structure type.

Investigation of the crystal structure of a low water content hydrous olivine to 29.9 GPa: A high-pressure single-crystal X-ray diffraction study

2020 ◽  
Vol 105 (12) ◽  
pp. 1857-1865
Author(s):  
Jingui Xu ◽  
Dawei Fan ◽  
Dongzhou Zhang ◽  
Bo Li ◽  
Wenge Zhou ◽  
...  
Keyword(s):  
High Pressure ◽  
Equation Of State ◽  
Single Crystal ◽  
Water Content ◽  
Structural Changes ◽  
Volume Data ◽  
Structural Refinement ◽  
X Ray Diffraction ◽  
X Ray ◽  
Water Contents

Abstract Olivine is the most abundant mineral in the Earth's upper mantle and subducting slabs. Studying the structural evolution and equation of state of olivine at high-pressure is of fundamental importance in constraining the composition and structure of these regions. Hydrogen can be incorporated into olivine and significantly influence its physical and chemical properties. Previous infrared and Raman spectroscopic studies indicated that local structural changes occur in Mg-rich hydrous olivine (Fo ≥ 95; 4883–9000 ppmw water) at high-pressure. Since water contents of natural olivine are commonly <1000 ppmw, it is inevitable to investigate the effects of such water contents on the equation of state (EoS) and structure of olivine at high-pressure. Here we synthesized a low water content hydrous olivine (Fo95; 1538 ppmw water) at low SiO2 activity and identified that the incorporated hydrogens are predominantly associated with the Si sites. We performed high-pressure single-crystal X-ray diffraction experiments on this olivine to 29.9 GPa. A third-order Birch-Murnaghan equation of state (BM3 EoS) was fit to the pressure-volume data, yielding the following EoS parameters: VT0 = 290.182(1) Å3, KT0 = 130.8(9) GPa, and K′T0 = 4.16(8). The KT0 is consistent with those of anhydrous Mg-rich olivine, which indicates that such low water content has negligible effects on the bulk modulus of olivine. Furthermore, we carried out the structural refinement of this hydrous olivine as a function of pressure to 29.9 GPa. The results indicate that, similar to the anhydrous olivine, the compression of the M1-O and M2-O bonds are comparable, which are larger than that of the Si-O bonds. The compression of M1-O and M2-O bonds of this hydrous olivine are comparable with those of anhydrous olivine, while the Si-O1 and Si-O2 bonds in the hydrous olivine are more compressible than those in the anhydrous olivine. Therefore, this study suggests that low water content has negligible effects on the EoS of olivine, though the incorporation of water softens the Si-O1 and Si-O2 bond.

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