Post-spinel transitions in pyrolite and Mg2SiO4 and akimotoite–perovskite transition in MgSiO3: Precise comparison by high-pressure high-temperature experiments with multi-sample cell technique

Ishii, Takayuki; Kojitani, Hiroshi; Akaogi, Masaki

doi:10.1016/j.epsl.2011.06.023

Cited by 82 publications

(114 citation statements)

References 41 publications

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“…The ab initio phase boundary is localized at slightly higher pressures (≈1-2 GPa) than those determined by other HP-HT experiments [124,127,129,130,133] (see Figure 11a). The calculated Clapeyron slope (i.e., dP/dT = −2.53 MPa/K) agrees well with those obtained by the most part of experimental investigations (ranging from −4.0 to −2.0 MPa/K) [121,[124][125][126][127]131,132,135], while other works [129,130,133,134] suggest a more gentle slope of the phase boundary (i.e., between −2.0 and −1.0 MPa/K or even less) (see Table 5). B3LYP results are in qualitative agreement with previous GGA calculations [137][138][139], whereas LDA [137] severely underestimates transformation pressures of the post-spinel reaction (see Figure 11b).…”

Section: Phase Equilibrium Calculation At Hp-ht: the Post-spinel Phassupporting

confidence: 74%

“…Ab initio B3LYP results show an excellent agreement with the in situ LH-DAC X-ray diffraction study of Shim et al [128] and the multi-anvil experiments of Ishii et al [132], as well as with calculations based on accurate calorimetric measurements by Akaogi and Ito [126] and Akaogi et al [131] (Figure 11a; see also Figure Table 5), although a recent study found a lower enthalpy of reaction [134]. The ab initio phase boundary is localized at slightly higher pressures (≈1-2 GPa) than those determined by other HP-HT experiments [124,127,129,130,133] (see Figure 11a).…”

Section: Phase Equilibrium Calculation At Hp-ht: the Post-spinel Phassupporting

confidence: 73%

“…The effect of lattice vibrations seems to be crucial to correctly predicting the high-pressure phase transformation; ab initio static enthalpy calculations [137][138][139]141] give transition pressures that are overestimated (by ≈1−2 up to 10 GPa) compared with those obtained by including vibrational contributions to thermodynamic properties (i.e., by minimizing Gibbs free energies instead of static enthalpies). [121,[124][125][126][127][128][129][130][131][132][133][134][135] and other ab initio calculations [137][138][139]. Figure 11.…”

Section: Phase Equilibrium Calculation At Hp-ht: the Post-spinel Phasmentioning

confidence: 99%

“…Owing to its geophysical implications, the Mg2SiO4 post-spinel phase transformations have been investigated by several experimental studies in the last decades [124][125][126][127][128][129][130][131][132][133][134][135]. Although experimental results are not consistent with each other concerning the P-T localization of the phase equilibrium boundary, there is general agreement about its most important thermodynamic feature; that is, the negative Clapeyron slope (i.e., dP/dT < 0) or endothermic character (i.e., ∆Hrxt > 0).…”

Section: Phase Equilibrium Calculation At Hp-ht: the Post-spinel Phasmentioning

confidence: 99%

See 3 more Smart Citations

First Principles Thermodynamics of Minerals at HP–HT Conditions: MgO as a Prototypical Material

Belmonte

2017

Minerals

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Ab initio thermodynamic properties, equation of state and phase stability of periclase (MgO, B1-type structure) have been investigated in a broad P-T range (0-160 GPa; 0-3000 K) in order to set a model reference system for phase equilibria simulations under deep Earth conditions. Phonon dispersion calculations performed on large supercells using the finite displacement method and in the framework of quasi-harmonic approximation highlight the performance of the Becke three-parameter Lee-Yang-Parr (B3LYP) hybrid density functional in predicting accurate thermodynamic functions (heat capacity, entropy, thermal expansivity, isothermal bulk modulus) and phase reaction boundaries at high pressure and temperature. A first principles Mie-Grüneisen equation of state based on lattice vibrations directly provides a physically-consistent description of thermal pressure and P-V-T relations without any need to rely on empirical parameters or other phenomenological formalisms that could give spurious anomalies or uncontrolled extrapolations at HP-HT. The post-spinel phase transformation, Mg 2 SiO 4 (ringwoodite) = MgO (periclase) + MgSiO 3 (bridgmanite), is taken as a computational example to illustrate how first principles theory combined with the use of hybrid functionals is able to provide sound results on the Clapeyron slope, density change and P-T location of equilibrium mineral reactions relevant to mantle dynamics.

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Section: Phase Equilibrium Calculation At Hp-ht: the Post-spinel Phassupporting

confidence: 74%

Section: Phase Equilibrium Calculation At Hp-ht: the Post-spinel Phassupporting

confidence: 73%

Section: Phase Equilibrium Calculation At Hp-ht: the Post-spinel Phasmentioning

confidence: 99%

Section: Phase Equilibrium Calculation At Hp-ht: the Post-spinel Phasmentioning

confidence: 99%

See 2 more Smart Citations

First Principles Thermodynamics of Minerals at HP–HT Conditions: MgO as a Prototypical Material

Belmonte

2017

Minerals

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“…2,3 This limitation is primarily a consequence of hardness of WC anvils. While for many years, the upper half of the lower mantle was considered relatively uninteresting; recent seismological studies 4 have shown that several subducted slabs penetrate into the lower mantle and stagnate at ∼1000 km, corresponding to 40 GPa.…”

Section: Introductionmentioning

confidence: 99%

Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils

Ishii

Shi

Rong

et al. 2016

Review of Scientific Instruments

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We have generated over 40 GPa pressures, namely, 43 and 44 GPa, at ambient temperature and 2000 K, respectively, using Kawai-type multi-anvil presses (KMAP) with tungsten carbide anvils for the first time. These high-pressure generations were achieved by combining the following pressure-generation techniques: (1) precisely aligned guide block systems, (2) high hardness of tungsten carbide, (3) tapering of second-stage anvil faces, (4) materials with high bulk modulus in a high-pressure cell, and (5)

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The postspinel boundary in pyrolitic compositions determined in the laser‐heated diamond anvil cell

Shim

et al. 2014

Geophys. Res. Lett.

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In situ multianvil press (MAP) studies have reported that the depth and the Clapeyron slope of the postspinel boundary are significantly less than those of the 660 km discontinuity inferred from seismic studies. These results have raised questions about whether the postspinel transition is associated with the discontinuity. We determined the postspinel transition in pyrolitic compositions in the laser‐heated diamond anvil cell (LHDAC) combined with in situ synchrotron X‐ray diffraction. The Clapeyron slope was determined to be −2.5 ± 0.4MPa/K and did not vary significantly with compositions and used pressure scales. Using Pt scales, our data indicate that the postspinel transition occurs in pyrolitic compositions at 23.6–24.5GPa (1850K). The transition pressure and slope are consistent with the depth and topography of the 660 km discontinuity. Our data reveal that inaccuracy in pressure scales alone cannot explain the discrepancy and technical differences between MAP and LHDAC contribute significantly to the discrepancy.

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Post-spinel transitions in pyrolite and Mg2SiO4 and akimotoite–perovskite transition in MgSiO3: Precise comparison by high-pressure high-temperature experiments with multi-sample cell technique

Cited by 82 publications

References 41 publications

First Principles Thermodynamics of Minerals at HP–HT Conditions: MgO as a Prototypical Material

First Principles Thermodynamics of Minerals at HP–HT Conditions: MgO as a Prototypical Material

Generation of pressures over 40 GPa using Kawai-type multi-anvil press with tungsten carbide anvils

The postspinel boundary in pyrolitic compositions determined in the laser‐heated diamond anvil cell

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