### Abstract

The P-V-T equation of state (EOS) for magnesium silicate perovskite (MgSiO_{3}) and periclase (MgO) was obtained by fitting measured P, V, T data. The EOS of MgSiO_{3} perovskite was determined by applying the Mie-Grüneisen-Debye approach, based on three alternative bulk modulus values (K_{T0} = 240, 250 and 261 GPa), yielding substantially different values for high-order thermoelastic parameters such as the Grüneisen parameter (γ) and the temperature derivative of bulk modulus ((∂K_{T}/∂T)_{P}). Combined with the EOS of magnesiowüstite, we calculated the density (ρ), bulk modulus (K_{S}) and seismic parameter (φ) for simplified pyrolitic lower mantle along a plausible adiabat (temperature at 670 km, T_{a} = 1900 K), and compared these values to those of a seismological model (PREM). The results based on K_{T0} of 261 GPa, which has been commonly used, showed good agreement with PREM, within 0.5% for ρ, and 2-3% for K_{S} and φ, throughout the lower mantle. The EOS obtained using the recent K_{T0} data (240-250 GPa), substantially overestimated K_{S} and φ by 5-10%, requiring a progressive enrichment in (Mg,Fe)O with increasing depth. In addition, a more realistic vibrational density of states (VDOS) model (Kieffer-type model) was applied to calculate the EOS. The effect of VDOS on thermoelastic parameters was not large enough to modify those conclusions.

Original language | English |
---|---|

Pages (from-to) | 87-95 |

Number of pages | 9 |

Journal | Physics of the Earth and Planetary Interiors |

Volume | 155 |

Issue number | 1-2 |

DOIs | |

Publication status | Published - Apr 14 2006 |

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### Keywords

- Equation of state
- Lower mantle
- Perovskite
- Thermoelastic parameters

### ASJC Scopus subject areas

- Geophysics
- Space and Planetary Science
- Physics and Astronomy (miscellaneous)
- Astronomy and Astrophysics

### Cite this

*Physics of the Earth and Planetary Interiors*,

*155*(1-2), 87-95. https://doi.org/10.1016/j.pepi.2005.10.002

**P-V-T equation of state of MgSiO3 perovskite and MgO periclase : Implication for lower mantle composition.** / Aizawa, Yoshitaka; Yoneda, Akira.

Research output: Contribution to journal › Article

*Physics of the Earth and Planetary Interiors*, vol. 155, no. 1-2, pp. 87-95. https://doi.org/10.1016/j.pepi.2005.10.002

}

TY - JOUR

T1 - P-V-T equation of state of MgSiO3 perovskite and MgO periclase

T2 - Implication for lower mantle composition

AU - Aizawa, Yoshitaka

AU - Yoneda, Akira

PY - 2006/4/14

Y1 - 2006/4/14

N2 - The P-V-T equation of state (EOS) for magnesium silicate perovskite (MgSiO3) and periclase (MgO) was obtained by fitting measured P, V, T data. The EOS of MgSiO3 perovskite was determined by applying the Mie-Grüneisen-Debye approach, based on three alternative bulk modulus values (KT0 = 240, 250 and 261 GPa), yielding substantially different values for high-order thermoelastic parameters such as the Grüneisen parameter (γ) and the temperature derivative of bulk modulus ((∂KT/∂T)P). Combined with the EOS of magnesiowüstite, we calculated the density (ρ), bulk modulus (KS) and seismic parameter (φ) for simplified pyrolitic lower mantle along a plausible adiabat (temperature at 670 km, Ta = 1900 K), and compared these values to those of a seismological model (PREM). The results based on KT0 of 261 GPa, which has been commonly used, showed good agreement with PREM, within 0.5% for ρ, and 2-3% for KS and φ, throughout the lower mantle. The EOS obtained using the recent KT0 data (240-250 GPa), substantially overestimated KS and φ by 5-10%, requiring a progressive enrichment in (Mg,Fe)O with increasing depth. In addition, a more realistic vibrational density of states (VDOS) model (Kieffer-type model) was applied to calculate the EOS. The effect of VDOS on thermoelastic parameters was not large enough to modify those conclusions.

AB - The P-V-T equation of state (EOS) for magnesium silicate perovskite (MgSiO3) and periclase (MgO) was obtained by fitting measured P, V, T data. The EOS of MgSiO3 perovskite was determined by applying the Mie-Grüneisen-Debye approach, based on three alternative bulk modulus values (KT0 = 240, 250 and 261 GPa), yielding substantially different values for high-order thermoelastic parameters such as the Grüneisen parameter (γ) and the temperature derivative of bulk modulus ((∂KT/∂T)P). Combined with the EOS of magnesiowüstite, we calculated the density (ρ), bulk modulus (KS) and seismic parameter (φ) for simplified pyrolitic lower mantle along a plausible adiabat (temperature at 670 km, Ta = 1900 K), and compared these values to those of a seismological model (PREM). The results based on KT0 of 261 GPa, which has been commonly used, showed good agreement with PREM, within 0.5% for ρ, and 2-3% for KS and φ, throughout the lower mantle. The EOS obtained using the recent KT0 data (240-250 GPa), substantially overestimated KS and φ by 5-10%, requiring a progressive enrichment in (Mg,Fe)O with increasing depth. In addition, a more realistic vibrational density of states (VDOS) model (Kieffer-type model) was applied to calculate the EOS. The effect of VDOS on thermoelastic parameters was not large enough to modify those conclusions.

KW - Equation of state

KW - Lower mantle

KW - Perovskite

KW - Thermoelastic parameters

UR - http://www.scopus.com/inward/record.url?scp=33644910909&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=33644910909&partnerID=8YFLogxK

U2 - 10.1016/j.pepi.2005.10.002

DO - 10.1016/j.pepi.2005.10.002

M3 - Article

AN - SCOPUS:33644910909

VL - 155

SP - 87

EP - 95

JO - Physics of the Earth and Planetary Interiors

JF - Physics of the Earth and Planetary Interiors

SN - 0031-9201

IS - 1-2

ER -