P-V-T equation of state of magnesiow�stite (Mg0.6Fe0.4)O

Fei, Yingwei; Mao, Ho‐kwang; Shu, Jinfu; Hu, J.

doi:10.1007/bf00200964

Cited by 108 publications

(54 citation statements)

References 20 publications

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“…The harmonic internal energy E(T, D ) is calculated from the Debye model (34). The model was based on Takemura's (23) room-temperature com- Table 1.…”

Section: Resultsmentioning

confidence: 99%

Toward an internally consistent pressure scale

Fei

Ricolleau

Frank

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

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622

498

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Our ability to interpret seismic observations including the seismic discontinuities and the density and velocity profiles in the earth's interior is critically dependent on the accuracy of pressure measurements up to 364 GPa at high temperature. Pressure scales based on the reduced shock-wave equations of state alone may predict pressure variations up to 7% in the megabar pressure range at room temperature and even higher percentage at high temperature, leading to large uncertainties in understanding the nature of the seismic discontinuities and chemical composition of the earth's interior. Here, we report compression data of gold (Au), platinum (Pt), the NaCl-B2 phase, and solid neon (Ne) at 300 K and high temperatures up to megabar pressures. Combined with existing experimental data, the compression data were used to establish internally consistent thermal equations of state of Au, Pt, NaCl-B2, and solid Ne. The internally consistent pressure scales provide a tractable, accurate baseline for comparing high pressuretemperature experimental data with theoretical calculations and the seismic observations, thereby advancing our understanding fundamental high-pressure phenomena and the chemistry and physics of the earth's interior.diamond-anvil cell ͉ high-pressure research ͉ pressure calibration ͉ thermodynamics ͉ x-ray diffraction T he earth has a layered internal structure with distinct boundaries. The boundaries of the five main layers (the upper mantle, the transition zone, the lower mantle, the liquid outer core, and the solid inner core) are well defined by the observed seismic velocity discontinuities at depths of 400, 670, 2,891, and 5,149 km (corresponding to pressures of 13.4, 23.8, 135.8, and 328.9 GPa, respectively) in a global average preliminary reference earth model (PREM) (1). The interpretation of these discontinuities requires experimental investigations of earth materials at high pressure and temperature. The seismic discontinuities near 400 and 670 km depth are commonly associated with the mineralogical phase transformations of (Mg,Fe) 2 SiO 4 from ␣-olivine to ␤-phase (wadsleyite) and from ␥-spinel (ringwoodite) to (Mg,Fe)SiO 3 -perovskite plus (Mg,Fe)O-magnesiowüstite, respectively (2). With the rapid increase in the use of broadband seismometers and seismic arrays, seismologists have been able to determine the depths of the 400-and 670-km discontinuities and their lateral variation with increasingly finer resolutions (3). To correlate the observed seismic variability with the compositional and thermal variations in the mantle, we have to be able to determine mantle phase transitions with high accuracy, better than 1% in pressure determination (i.e., Ϯ0.25 GPa at 25 GPa). Similarly, it is critically dependent on the accuracy in pressure determination whether or not the recently discovered postperovskite transition (4, 5) indeed occurs at the base of the lower mantle and accounts for a number of seismic anomalies observed in the DЉ region. Because the DЉ layer is observed in a narrow depth int...

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“…The harmonic internal energy E(T, D ) is calculated from the Debye model (34). The model was based on Takemura's (23) room-temperature com- Table 1.…”

Section: Resultsmentioning

confidence: 99%

Toward an internally consistent pressure scale

Fei

Ricolleau

Frank

et al. 2007

Proc. Natl. Acad. Sci. U.S.A.

Self Cite

622

498

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“…Following the definition of the employed EOS, the model has a fixed value of K'=dK/dP=4, the first pressure derivative of the isothermal bulk modulus (K). By knowing the volume or lattice parameters at ambient conditions, we can extract the composition of the material [24,[26][27][28].…”

Section: A Compressibility Of Fpmentioning

confidence: 99%

Critical behavior of Mg1–xFexO at the pressure-induced iron spin-state crossover

Glazyrin¹,

Sinmyo²,

Bykova³

et al. 2017

Phys. Rev. B

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“…Laboratory studies are now available that address these issues. In the past 5 years, equation of state studies using synchrotron X ray sources to measure density at high pressure and temperature in both the diamond anvil cells and in multi-anvil devices have matured [Fei et al, 1992;Wang et al, 1998a]. Phase equilibria studies have quantified phase transformations in simple chemical systems as well as complicated systems at the extreme pressures and temperatures of the 660 km discontinuity using multi-anvil devices.…”

Section: Introductionmentioning

confidence: 99%

Chemical‐ and Clapeyron‐induced buoyancy at the 660 km discontinuity

Weidner¹,

Wang²

1998

J. Geophys. Res.

132

109

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Abstract. The impact of phase equilibria and equation of state measurements on defining the buoyancy associated with the 660 km discontinuity is examined. Aluminum has a striking effect on the sequence of phase transitions expected at 660 km. With a pyrolite chemistry the sign of the phase transition contribution to buoyancy depends on temperature, with convection-assisting forces being victorious in hotter regions. Lower A1 and/or temperature result in the perovskite-forming transformation resisting convection but with a much reduced magnitude compared with a pure olivine mantle. Density considerations suggest that there is no positive evidence for chemical-induced buoyancy across the 660 km discontinuity. The surface processing which forms a basaltic crust will cause a density contrast that assists convection in the transition zone but resists convection through the expanded garnet stability field of mid-ocean ridge basalt. The detailed seismic character of the 660 km depth region and its lateral variations hold the key to defining the location of the mantle state relative to the parameter space defined by A1 and temperature in this study. 15=-• vi(Api)(Oz/OP)(OP/OT)iAT (2)where vi is the volume percent of the i th phase, A pi is the density increase associated with the transition, 0z/0P is the factor converting depth to pressure, OP/OT is the Clapeyron slope of the phase boundary, and A T is the excess temperature associated with the density anomaly. A negative value of 15/AT will enhance convection, while a positive value will impede it.The sign of the Clapeyron slope for the transition from spinel to perovskite and magnesiowustite is generally considered to be negative. Navrotsky [1980] provided thermodynamic reasons for such a negative slope, while Ito and Yamada [1982] and Ito and Takahashi [1989] confirmed this possibility experimentally. Calorimetric data by Ito et al. [1990] and more recentlyAkaogi and Ito [1993a, b], combined with phase equilibria observations, serve to estimate the P-T Clapeyron slope of the phase boundary separating these two fields as about -3 MPa/K. Since this transition involves a density increase of ---6%, it provides a buoyancy force that opposes convection. However, even in a pyrolite mantle, spinel will constitute <60% of the volume at this depth. The remainder of the material includes a majoritic-enriched garnet along with a Ca-bearing perovskite. The garnet (---30% in volume) will also undergo a transition to perovskite in the 660 km region with a density increase about twice as large as that for spinel, while the Ca-perovskite will already be in its stable lower mantle phase.In contrast to the olivine component the pyroxene-garnet system has positive Clapeyron slopes for the perovskiteforming phase transition. The results of Yusa et al. [1993], based on thermochemical and phase equilibria data, suggest a slope for the garnet-to-perovskite transition of---5 MPa/K for a partially disordered tetragonal garnet. Figure 1 illustrates the phase boundaries for the MgSiO 3 ta...

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P-V-T equation of state of magnesiow�stite (Mg0.6Fe0.4)O

Cited by 108 publications

References 20 publications

Toward an internally consistent pressure scale

Toward an internally consistent pressure scale

Critical behavior of Mg1–xFexO at the pressure-induced iron spin-state crossover

Chemical‐ and Clapeyron‐induced buoyancy at the 660 km discontinuity

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