The elasticity of the MgSiO3 post-perovskite phase in the Earth's lowermost mantle

T. Iitaka, K. Hirose, K. Kawamura, M. Murakami

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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.

Original languageEnglish
Pages (from-to)442-445
Number of pages4
JournalNature
Volume430
Issue number6998
DOIs
Publication statusPublished - Jul 22 2004

ASJC Scopus subject areas

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    Iitaka, T., Hirose, K., Kawamura, K., & Murakami, M. (2004). The elasticity of the MgSiO3 post-perovskite phase in the Earth's lowermost mantle. Nature, 430(6998), 442-445. https://doi.org/10.1038/nature02702