### Abstract

Room temperature static compression of MgO (periclase) was performed under nearly hydrostatic conditions using energy dispersive synchrotron X-ray diffraction in a diamond anvil cell with methanol-ethanol (to 10 GPa) or helium (to 52 GPa) as a pressuretransmitting medium. Highly precise cell parameters were determined with an average relative standard deviation = 0.0003 over all the experimental pressure range. Fixing the bulk modulus K_{OT}= 160.2 GPa, a fit of the data to the third-order BirchMurnaghan equation of state yields: V_{0} = 74.71 ± 0.01 Å^{3},(∂K_{0T}/∂P)_{r}=3.99±0.01. Afit of different P-V-T datasets, ranging to 53 GPa and 2500 K, to a Birch-Murnaghan-Debye thermal equation of state constrained the Grüneisen parameter γ_{0} = 1.49 ± 0.03, but not its volume dependence q, which was constrained to 1.65 ± 0.4 by thermodynamic theory. A model based on a constant value of q cannot explain the ultrahigh pressure (P = 174-203 GPa) shock compression data. We developed a model in which q decreases with compression from 1.65 at 0.1 MPa to 0.01 at 200 GPa. This model, within the framework of the Mie-Gruneisen-Debye assumptions, satisfactorily describes the low-pressure static data = 0.4% to 53 GPa) and the high-pressure Hugoniot data (1% to 203 GPa). Average values of the thermal expansion coefficient α range between 14.1 ± 2.8 and 16.3 ± 2.7 × 10^{-6} K^{-1} P = 174-203 GPa. The pressure dependence of the melting temperature yields an initial pressure derivative ∂T_{m}/∂P = 98 K/GPa. Our analysis shows that it is possible to develop a simple model of the volume dependence of the Grüneisen parameter that can successfully describe the P-V-T equation of state of MgO from ambient conditions to 203 GPa and 3663 K.

Original language | English (US) |
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Pages (from-to) | 515-528 |

Number of pages | 14 |

Journal | Journal of Geophysical Research: Solid Earth |

Volume | 106 |

Issue number | B1 |

DOIs | |

State | Published - 2001 |

### All Science Journal Classification (ASJC) codes

- Geophysics
- Geochemistry and Petrology
- Earth and Planetary Sciences (miscellaneous)
- Space and Planetary Science

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## Cite this

*Journal of Geophysical Research: Solid Earth*,

*106*(B1), 515-528. https://doi.org/10.1029/2000jb900318