High-pressure phase transitions of clinoenstatite

Lazarz, John D.; Dera, Przemysław; Hu, Yi; Meng, Yue; Bina, Craig R.; Jacobsen, S. D.

doi:10.2138/am-2019-6740

Cited by 11 publications

(13 citation statements)

References 44 publications

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“…This makes the pOEn- P 2 1 / c phase very different from a further HP clinopyroxene phase, which also crystallizes in P 2 1 / c but has the M+ M+ sequence typical for clinopyroxene phases and is confirmed by the HP -CEn2- P 2 1 / c structures of various silicate clinopyroxenes. 30 − 32 …”

Section: Resultsmentioning

confidence: 99%

“…A comparable distinction has to be made for the P 2 1 / c pyroxenes, where, in addition to the low-clinopyroxene form (LCEn- P 2 1 / c 28 ), HP variants (referred to as “ HP -CEn2” or “ HP - P 2 1 / c ” in the literature) have recently been found for several representatives. 29 − 32 …”

Section: Introductionmentioning

confidence: 99%

“… 25 , 26 , 37 At considerably higher pressures, HP -CEn- C 2/ c structures undergo a further pressure-induced transition to the so-called “ HP - P 2 1 / c ” (here further referred to as HP -CEn2- P 2 1 / c ), whereby part of the T cations transform to a 6-fold octahedral coordination. 30 − 32 …”

Section: Introductionmentioning

confidence: 99%

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P2₁/c Postorthopyroxene γ-LiScGe₂O₆, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure

et al. 2020

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Orthorhombic β-LiScGe 2 O 6 single crystals were compressed hydrostatically up to 10.35 GPa using a diamond anvil cell and investigated in situ by means of X-ray diffraction and Raman spectroscopy. Crystal-structure investigations at ambient conditions and at high pressure show a structural transition from an orthopyroxene-type Pbca structure ( a ≈ 18.43 Å, b ≈ 8.85 Å, and c ≈ 5.34 Å at 8.6 ± 0.1 GPa) to a postorthopyroxene type P 2 1 / c structure of the new dense γ-LiScGe 2 O 6 ( a ≈ 18.62 Å, b ≈ 8.85 Å, c ≈ 5.20 Å, and β ≈ 93.1° at 9.5 ± 0.1 GPa). The structure refinements reveal displacive shifts of O atoms associated with a rotation of every other tetrahedral-chain unit from the O- to S-type position similar to the postorthopyroxene-type MgSiO 3 . As a consequence of the oxygen displacement, the coordination number of Li atoms is changing from [5 + 1] to a proper 6-fold coordination. The transition around P c = 9.0 ± 0.1 GPa is associated with a volume discontinuity of Δ V = −1.6%. This orthopyroxene (OEn- Pbca ) to postorthopyroxene (pOEn- P 2 1 / c ) transition is the second example of this type of transformation. Precise lattice parameters have been determined during isothermal compression. The fit of the unit-cell volumes of β -LiScGe 2 O 6 , using a third-order Birch–Murnaghan equation of state, yields V 0 = 943.63 ± 0.11 Å 3 , K 0 = 89.8 ± 0.6 GPa, and d K /d P = 4.75 ± 0.18 as parameters. Evaluation of the data points beyond the critical transition pressure using a second-order Birch–Murnaghan equation suggests V 0 = 940.6 ± 4.4 Å 3 and K 0 = 82.4 ± 4.8 GPa. A series of high-pressure Raman spectra confirm the symmetry-related structural transition, with band positions shifting in a noncontinuous manner, thus confirming the proposed first-order transition.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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P2₁/c Postorthopyroxene γ-LiScGe₂O₆, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure

et al. 2020

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“…The HP polymorph represents the thermodynamic stable structure of enstatite at mantle conditions. Despite the relevance of these phases, only few data on the elastic and structural behavior of HP clinoenstatite above 10 GPa exist (Lazarz et al, 2019). We report here crystal structure refinements of P2 1 /c and C2/c clinoenstatite in the pressure interval 0-20 GPa.…”

Section: Sample Alignment Single-crystal X-ray Diffraction Data Collection and Data Processingmentioning

confidence: 94%

“…We report here crystal structure refinements of P2 1 /c and C2/c clinoenstatite in the pressure interval 0-20 GPa. The results are compared with those of Lazarz et al (2019).…”

Section: Sample Alignment Single-crystal X-ray Diffraction Data Collection and Data Processingmentioning

confidence: 99%

Single-crystal diffraction at the high-pressure Indo-Italian beamline Xpress at Elettra, Trieste

et al. 2020

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In this study the first in situ high-pressure single-crystal X-ray diffraction experiments at Xpress, the Indo-Italian beamline of the Elettra synchrotron, Trieste (Italy), are reported. A description of the beamline experimental setup and of the procedures for single-crystal centring, data collection and processing, using diamond anvil cells, are provided. High-pressure experiments on a synthetic crystal of clinoenstatite (MgSiO3), CaCO3 polymorphs and a natural sample of leucophoenicite [Mn7Si3O12(OH)2] validated the suitability of the beamline experimental setup to: (i) locate and characterize pressure-induced phase transitions; (ii) solve ab initio the crystal structure of high-pressure polymorphs; (iii) perform fine structural analyses at the atomic scale as a function of pressure; (iv) disclose complex symmetry and structural features undetected using conventional X-ray sources.

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Discovering High-Pressure and High-Temperature Minerals

Tschauner

Ma²

2023

Celebrating the International Year of Mineralogy

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High-pressure phase transitions of clinoenstatite

Cited by 11 publications

References 44 publications

P2₁/c Postorthopyroxene γ-LiScGe₂O₆, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure

P2₁/c Postorthopyroxene γ-LiScGe₂O₆, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure

Single-crystal diffraction at the high-pressure Indo-Italian beamline Xpress at Elettra, Trieste

Discovering High-Pressure and High-Temperature Minerals

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High-pressure phase transitions of clinoenstatite

Cited by 11 publications

References 44 publications

P21/c Postorthopyroxene γ-LiScGe2O6, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure

P21/c Postorthopyroxene γ-LiScGe2O6, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure

Single-crystal diffraction at the high-pressure Indo-Italian beamline Xpress at Elettra, Trieste

Discovering High-Pressure and High-Temperature Minerals

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P2₁/c Postorthopyroxene γ-LiScGe₂O₆, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure

P2₁/c Postorthopyroxene γ-LiScGe₂O₆, a New Dense High-Pressure Polymorph and Its Direct Transformation from the Pbca Structure