## Abstract

Large-scale first-principles density functional theory (DFT) calculations have been carried out to investigate how Al^{3+} can be incorporated into MgSiO_{3} perovskite under high pressure and to study the resultant change in the compressional mechanism of MgSiO_{3} perovskite. We examined two types of MgSiO_{3} models with 6.25 mol% Al_{2}O_{3}: charge-coupled substitution and oxygen-vacancy mechanisms. Five pressure points from 0 to 100 GPa have been considered. At each pressure point, we have calculated five models of the oxygen vacancy and five models of the charge-coupled mechanisms. We also change the internal positions of the substituted Al in the calculated cells, which have 80 atoms. Our free energy calculations show Al^{3+} replaces the nearest-neighbor cation pairs (Mg^{2+} and Si^{4+}) at all pressures investigated. The calculated bulk modulus of the most energetically favorable model is 3.4% lower than that of the Al-free MgSiO_{3} perovskite. These results may have important implications for discriminating between thermal and compositional effects of 1-D Earth models and the possible influence of aluminum perovskite.

Original language | English |
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Pages (from-to) | 617-625 |

Number of pages | 9 |

Journal | Earth and Planetary Science Letters |

Volume | 206 |

Issue number | 3-4 |

DOIs | |

Publication status | Published - 2003 Feb 15 |

Externally published | Yes |

## Keywords

- Aluminous perovskite
- Bulk modulus
- First-principles calculations
- Substitution mechanism

## ASJC Scopus subject areas

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