Compressional behavior of strontianite SrCO3 by synchrotron X-ray radiation diffraction: effects of pressure transmitting media
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The compressional behavior of strontianite SrCO3 was investigated at ambient temperature and high pressure, using a diamond anvil cell (DAC) with Ne as a pressure transmitting medium. X-ray diffraction patterns were collected to ~52 GPa using in situ angle-dispersive synchrotron-based powder X-ray diffraction (XRD). A phase transition was observed at ~20 GPa, and no indications of further transitions were detected up to ~52 GPa. The pressure-volume (P-V) data within 0.27-17.35 GPa were fitted to a third-order Birch-Murnaghan equation of state (BM3 EoS) to obtain the elastic coefficients including zero-pressure unit-cell volume, isothermal bulk modulus and its pressure derivative: V0 = 258.4(3) Å3, KT0 = 55(2) GPa, and K'T0 = 4.3(3). The V0 and KT0 were obtained as 258.1(2) Å3 and 57.1(6) GPa, when fixed K'T0 = 4. The axial compressional behavior of strontianite was also investigated by fitting the pressure-lattice parameter data to a parameterized form of the BM3 EoS, and the compression of the a-, b-, and c-axis was strongly anisotropic, with Ka0 = 104(6), Kb0 = 52(12), and Kc0 = 31.6(5) GPa. Based on this and previous studies using different pressure transmitting media (PTM), the effects PTM on the compressional behavior of strontianite were discussed.Keywords:
Powder Diffraction
Diamond anvil cell
Isothermal process
The equation of state of KCl and KBr, compressed in a helium pressure medium in a diamond-anvil cell, has been measured by x-ray diffraction in the B1 and B2 phases up to 165 GPa at 298 K. The $P$-$V$-$T$ of B2 KCl and B2 KBr has been calculated by ab initio molecular dynamics in a wide compression range and up to 7000 K. The thermal pressure exhibits a linear behavior with temperature and remains low under high compression. The experimental $P$-$V$ points and the thermal pressure calculated by molecular dynamics have been used to set up a high-pressure--high-temperature equation of state of B2 KCl and B2 KBr. With these equations of state, B2 KCl and B2 KBr can be used as pressure markers in laser-heated diamond-anvil-cell experiments.
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Atmospheric temperature range
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Hydrostatic pressure
Hydrostatic equilibrium
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Grüneisen parameter
Outer core
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Experimental high-pressure X-ray diffraction studies have been performed on ThN powder for pressures up to 47 GPa using synchrotron radiation and a diamond anvil cell. The bulk modulus B0 and its pressure derivative B′0 have been determined: B0 = 175(15) GPa and B'0 = 4.0(4). No structural phase transition has been found in contrast to UN studied previously.
Diamond anvil cell
Powder Diffraction
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The stability and equation of state of the post‐perovskite phase in MgGeO 3 were investigated to 2 Mbar by in situ x‐ray diffraction experiments using the laser‐heated diamond cell as well as by theoretical calculations using density functional theory. The stability of the phase was demonstrated at 92‐201 GPa during laser heating. By using the Birch‐Murnaghan equation of state, we obtained a zero‐pressure volume ( V 0 ) of 179.2 ± 0.7 Å 3 , bulk modulus ( K 0 ) of 207 ± 5 GPa with a pressure derivative ( K ′ 0 ) of 4.4 from experiments at room temperatures, and V 0 = 178.02 Å 3 , K 0 = 201.9 GPa, K ′ 0 = 4.34 from theoretical calculations at 0 K. The relative axial compressibilities of the silicate and germanate post‐perovskite phases are similar although MgSiO 3 is more anisotropic than MgGeO 3 .
Germanate
Diamond anvil cell
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