Title |
The elasticity of the MgSiO3 post-perovskite phase in the Earth's lowermost mantle
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Published in |
Nature, July 2004
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DOI | 10.1038/nature02702 |
Pubmed ID | |
Authors |
T. Iitaka, K. Hirose, K. Kawamura, M. Murakami |
Abstract |
MgSiO3 perovskite has been assumed to be the dominant component of the Earth's lower mantle, although this phase alone cannot explain the discontinuity in seismic velocities observed 200-300 km above the core-mantle boundary (the D" discontinuity) or the polarization anisotropy observed in the lowermost mantle. Experimental and theoretical studies that have attempted to attribute these phenomena to a phase transition in the perovskite phase have tended to simply confirm the stability of the perovskite phase. However, recent in situ X-ray diffraction measurements have revealed a transition to a 'post-perovskite' phase above 125 GPa and 2,500 K--conditions close to those at the D" discontinuity. Here we show the results of first-principles calculations of the structure, stability and elasticity of both phases at zero temperature. We find that the post-perovskite phase becomes the stable phase above 98 GPa, and may be responsible for the observed seismic discontinuity and anisotropy in the lowermost mantle. Although our ground-state calculations of the unit cell do not include the effects of temperature and minor elements, they do provide a consistent explanation for a number of properties of the D" layer. |
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Student > Ph. D. Student | 26 | 18% |
Professor | 18 | 13% |
Professor > Associate Professor | 15 | 11% |
Student > Master | 15 | 11% |
Other | 16 | 11% |
Unknown | 19 | 13% |
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Other | 6 | 4% |
Unknown | 25 | 18% |