X-ray diffraction investigations of CaF<sub>2</sub> at high pressure

Gerward, L.; Olsen, J. Staun; Steenstrup, S.; Malinowski, M.; Åsbrink, Stig; Waśkowska, A.

doi:10.1107/s0021889892004096

Cited by 104 publications

(89 citation statements)

References 9 publications

(11 reference statements)

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“…Our average precisions in volume for the two materials (1 part in 12 500 for fluorite, 1 part in 9000 for quartz) yield much closer precisions in pressure, with quartz being marginally better for pressure determination at lower pressures and marginally worse than fluorite at 9 GPa. Thus, quartz is more suited to pressure measurement at low pressures and, of course, can be used at pressures in excess of the limit of 9.2 GPa at which fluorite undergoes a phase transition which is destructive of single crystals (Gerward et al, 1992).…”

Section: Discussionmentioning

confidence: 99%

The Use of Quartz as an Internal Pressure Standard in High-Pressure Crystallography

Angel¹,

Allan²,

Miletich³

et al. 1997

J Appl Crystallogr

360

232

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The unit-cell parameters of quartz, SiO2, have been determined by single-crystal diffraction at 22 pressures to a maximum pressure of 8.9 GPa (at room temperature) with an average precision of 1 part in 9000. Pressure was determined by the measurement of the unit-cell volume of CaF2 fluorite included in the diamond-anvil pressure cell. The variation of quartz unit-cell parameters with pressure is described by: a-4.91300 (11) = -0.0468 (2) P + 0.00256 (7) P~--0.000094 (6) p3, c -5.40482 (17) = -0.03851 (2) P + 0.00305 (7) p2 _ 0.000121 (6)/>3, where P is in GPa and the cell parameters are in ~ngstroms. The volume-pressure data of quartz are described by a Birch-Murnaghan thirdorder equation of state with parameters V0= 112.981 (2) ~3, KT0 = 37.12 (9) GPa and K' = 5.99 (4). Refinement of K" in a fourth-order equation of state yielded a value not significantly different from the value implied by the third-order equation. The use of oriented quartz single crystals is proposed as an improved internal pressure standard for high-pressure single-crystal diffraction experiments in diamond-anvil cells. A measurement precision of 1 part in 10 000 in the volume of quartz leads to a precision in pressure measurement of 0.009 GPa at 9 GPa.

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Section: Discussionmentioning

confidence: 99%

The Use of Quartz as an Internal Pressure Standard in High-Pressure Crystallography

Angel¹,

Allan²,

Miletich³

et al. 1997

J Appl Crystallogr

360

232

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“…The mechanism for the antifluorite-anticotunnite phase transition is already well understood because of the numerous well-known pressure-induced fluorite-cotunnite transitions that occur [23,24]. If one pictures the antifluorite structure as (111) planes of anions separated by pairs of (111) planes composed of ions from the cation sublattice, the mechanism for the transition can be seen as a displacement of the anions in the [111] directions, half to the adjacent upper plane and half to the adjacent lower plane, accompanied by rotations and distortions of the Li triangular polyhedra within the planes (Fig.…”

Section: Discussionmentioning

confidence: 99%

Pressure-induced antifluorite-to-anticotunnite phase transition in lithium oxide

et al. 2006

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Using synchrotron angle-dispersive x-ray diffraction (ADXD) and Raman spectroscopy on samples of Li 2 O pressurized in a diamond anvil cell, we observed a reversible phase change from the cubic antifluorite (α, Fm-3m) to orthorhombic anticotunnite (β, Pnma) phase at 50(±5) GPa at ambient temperature. This transition is accompanied by a relatively large volume collapse of 5.4 (±0.8) % and large hysteresis upon pressure reversal (P down at ∼25 GPa). Contrary to a recent study, our data suggest that the high-pressure β-phase (B o = 188±12 GPa) is substantially stiffer than the low-pressure α-phase (B o = 90±1 GPa). A relatively strong and pressure-dependent preferred orientation in β-Li 2 O is observed. The present result is in accordance with the systematic behavior of antifluorite-to-anticotunnite phase transitions occurring in the alkali-metal sulfides.

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“…[49,51,52,55,57,[61][62][63][64]). Cubic F m3m is known to transform into the orthorhombic P nma phase at a pressure between 8 and 10 GPa, accompanied by an increase of the coordination number of Ca from 8 to 9.…”

Section: A Bulk Propertiesmentioning

confidence: 99%

“…Cubic F m3m is known to transform into the orthorhombic P nma phase at a pressure between 8 and 10 GPa, accompanied by an increase of the coordination number of Ca from 8 to 9. X-ray diffraction and Raman spectroscopy have shown that this high pressure phase is stable up to 49 GPa at room temperature 49,51 . In Fig.…”

Section: A Bulk Propertiesmentioning

confidence: 99%

High accuracy and transferability of a neural network potential through charge equilibration for calcium fluoride

et al. 2017

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We investigate the accuracy and transferability of a recently developed high dimensional neural network (NN) method for calcium fluoride, fitted to a database of ab initio density functional theory (DFT) calculations based on the Perdew-Burke-Ernzerhof (PBE) exchange correlation functional. We call the method charge equilibration via neural network technique (CENT). Although the fitting database contains only clusters (i.e. non-periodic structures), the NN scheme accurately describes a variety of bulk properties. In contrast to other available empirical methods the CENT potential has a much simpler functional form, nevertheless it correctly reproduces the PBE energetics of various crystalline phases both at ambient and high pressure. Surface energies and structures as well as dynamical properties derived from phonon calculations are also in good agreement with PBE results. Overall, the difference between the values obtained by the CENT potential and the PBE reference values is less than or equal to the difference between the values of local density approximation (LDA) and Born-Mayer-Huggins (BMH) with those calculated by the PBE exchange correlation functional.

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X-ray diffraction investigations of CaF₂ at high pressure

Cited by 104 publications

References 9 publications

The Use of Quartz as an Internal Pressure Standard in High-Pressure Crystallography

The Use of Quartz as an Internal Pressure Standard in High-Pressure Crystallography

Pressure-induced antifluorite-to-anticotunnite phase transition in lithium oxide

High accuracy and transferability of a neural network potential through charge equilibration for calcium fluoride

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X-ray diffraction investigations of CaF2 at high pressure

Cited by 104 publications

References 9 publications

The Use of Quartz as an Internal Pressure Standard in High-Pressure Crystallography

The Use of Quartz as an Internal Pressure Standard in High-Pressure Crystallography

Pressure-induced antifluorite-to-anticotunnite phase transition in lithium oxide

High accuracy and transferability of a neural network potential through charge equilibration for calcium fluoride

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X-ray diffraction investigations of CaF₂ at high pressure