Crystal structure and thermoelastic properties of (Mg0.91Fe 0.09)SiO3 postperovskite up to 135 GPa and 2,700 K

Sang Heon Shim, Krystle Catalli, Justin Hustoft, Atsushi Kubo, Vitali B. Prakapenka, Wendel A. Caldwell, Martin Kunz

Research output: Contribution to journalArticlepeer-review

45 Scopus citations

Abstract

Intriguing seismic observations have been made for the bottom 400 km of Earth's mantle (the D″ region) over the past few decades, yet the origin of these seismic structures has not been well understood. Recent theoretical calculations have predicted many unusual changes in physical properties across the postperovskite transition, perovskite (Pv) → postperovskite (PPv), that may provide explanations for the seismic observations. Here, we report measurements of the crystal structure of (Mg0.91Fe 0.09)SiO3-PPv under quasi-hydrostatic conditions up to the pressure (P)-temperature (T) conditions expected for the core-mantle boundary (CMB). The measured crystal structure is in excellent agreement with the first-principles calculations. We found that bulk sound speed (V Φ) decreases by 2.4 ± 1.4% across the PPv transition. Combined with the predicted shear-wave velocity (VS) increase, our measurements indicate that lateral variations in mineralogy between Pv and PPv may result in the anticorrelation between the VΦ and VS anomalies at the D″ region. Also, density increases by 1.6 ± 0.4% and Grüneisen parameter decreases by 21 ± 15% across the PPv transition, which will dynamically stabilize the PPv lenses observed in recent seismic studies.

Original languageEnglish (US)
Pages (from-to)7382-7386
Number of pages5
JournalProceedings of the National Academy of Sciences of the United States of America
Volume105
Issue number21
DOIs
StatePublished - May 27 2008

Keywords

  • Bulk sound speed
  • Equation of state
  • Grüneisen parameter
  • Mantle
  • Phase transition

ASJC Scopus subject areas

  • General

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