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The elasticity of the MgSiO3 post-perovskite phase in the Earth's lowermost mantle | | T Iitaka
; K Hirose
; K Kawamura
; M Murakami
; | | Date: |
22 Jul 2004 | | Journal: | Nature, 430 (6998), 442-5 | | 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. | | Source: | PubMed, pmid15269765 doi: 10.1038/nature02702 | | Services: | Forum | Review | Favorites | |
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