### Abstract

Results are presented of an ab initio study of the structure and thermoelastic properties of orthorhombic (Pbnm) MgSiO_{3} perovskite as a function of T and P. Self-consistent free energies are computed using quasi-harmonic lattice dynamics, with interatomic potentials derived from an electron-gas formation. At high T the orthorhombic phase undergoes successive second-order transitions to tetragonal and cubic phases. The transition T increases with P, such that the orthorhombic phase is stable throughout most of the lower mantle, although higher symmetry phases could occur near the top of the lower mantle. At zero P the calculated bulk modulus and thermal expansion are in excellent agreement with available data. For high-T isotherms, a finite-strain decompression of the high-P equation of state of perovskite substantially overestimates its zero-P density and bulk modulus; hence constraints on the chemical composition of the lower mantle, based on a comparison of the decompressed seismological properties with zero-P laboratory data, may significantly overestimate the proportion of perovskite in the lower mantle. (Authors' abstract)-C.N.

Original language | English (US) |
---|---|

Pages (from-to) | 809-812 |

Number of pages | 4 |

Journal | Geophysical Research Letters |

Volume | 12 |

Issue number | 12 |

State | Published - 1985 |

Externally published | Yes |

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### ASJC Scopus subject areas

- Earth and Planetary Sciences (miscellaneous)

### Cite this

_{3}perovskite.

*Geophysical Research Letters*,

*12*(12), 809-812.

**Ab initio structural and thermoelastic properties of orthorhombic MgSiO _{3} perovskite.** / Wolf, George; Bukowinski, M. S T.

Research output: Contribution to journal › Article

_{3}perovskite.',

*Geophysical Research Letters*, vol. 12, no. 12, pp. 809-812.

_{3}perovskite. Geophysical Research Letters. 1985;12(12):809-812.

}

TY - JOUR

T1 - Ab initio structural and thermoelastic properties of orthorhombic MgSiO3 perovskite.

AU - Wolf, George

AU - Bukowinski, M. S T

PY - 1985

Y1 - 1985

N2 - Results are presented of an ab initio study of the structure and thermoelastic properties of orthorhombic (Pbnm) MgSiO3 perovskite as a function of T and P. Self-consistent free energies are computed using quasi-harmonic lattice dynamics, with interatomic potentials derived from an electron-gas formation. At high T the orthorhombic phase undergoes successive second-order transitions to tetragonal and cubic phases. The transition T increases with P, such that the orthorhombic phase is stable throughout most of the lower mantle, although higher symmetry phases could occur near the top of the lower mantle. At zero P the calculated bulk modulus and thermal expansion are in excellent agreement with available data. For high-T isotherms, a finite-strain decompression of the high-P equation of state of perovskite substantially overestimates its zero-P density and bulk modulus; hence constraints on the chemical composition of the lower mantle, based on a comparison of the decompressed seismological properties with zero-P laboratory data, may significantly overestimate the proportion of perovskite in the lower mantle. (Authors' abstract)-C.N.

AB - Results are presented of an ab initio study of the structure and thermoelastic properties of orthorhombic (Pbnm) MgSiO3 perovskite as a function of T and P. Self-consistent free energies are computed using quasi-harmonic lattice dynamics, with interatomic potentials derived from an electron-gas formation. At high T the orthorhombic phase undergoes successive second-order transitions to tetragonal and cubic phases. The transition T increases with P, such that the orthorhombic phase is stable throughout most of the lower mantle, although higher symmetry phases could occur near the top of the lower mantle. At zero P the calculated bulk modulus and thermal expansion are in excellent agreement with available data. For high-T isotherms, a finite-strain decompression of the high-P equation of state of perovskite substantially overestimates its zero-P density and bulk modulus; hence constraints on the chemical composition of the lower mantle, based on a comparison of the decompressed seismological properties with zero-P laboratory data, may significantly overestimate the proportion of perovskite in the lower mantle. (Authors' abstract)-C.N.

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M3 - Article

AN - SCOPUS:0022265077

VL - 12

SP - 809

EP - 812

JO - Geophysical Research Letters

JF - Geophysical Research Letters

SN - 0094-8276

IS - 12

ER -