Reports

Structure and Freezing of MgSiO₃ Liquid in Earth's Lower Mantle

Lars Stixrude^1* and Bijaya Karki²

First-principles molecular-dynamics simulations show that over the pressure regime of Earth's mantle the mean silicon-oxygen coordination number of magnesium metasilicate liquid changes nearly linearly from 4 to 6. The density contrast between liquid and crystal decreases by a factor of nearly 5 over the mantle pressure regime and is 4% at the core-mantle boundary. The ab initio melting curve, obtained by integration of the Clausius-Clapeyron equation, yields a melting temperature at the core-mantle boundary of 5400 ± 600 kelvins.

¹ Department of Earth and Planetary Science, University of California, Berkeley, CA 94720, USA.
² Department of Computer Science, Louisiana State University, Baton Rouge, LA 70803, USA.

^* On leave from Department of Geological Sciences, University of Michigan, Ann Arbor, MI 48109, USA.

To whom correspondence should be addressed. E-mail: stixrude{at}umich.edu

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X-ray Raman scattering study of MgSiO3 glass at high pressure: Implication for triclustered MgSiO3 melt in Earth's mantle.

S. K. Lee, J.-F. Lin, Y. Q. Cai, N. Hiraoka, P. J. Eng, T. Okuchi, H.-k. Mao, Y. Meng, M. Y. Hu, P. Chow, et al. (2008)
PNAS 105, 7925-7929
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Evidence for anomalously large degree of polymerization in Mg2SiO4 glass and melt.

S. Sen and J. Tangeman (2008)
American Mineralogist 93, 946-949
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High-pressure structure and bonding in CaIrO3: The structure model of MgSiO3 post-perovskite investigated with time-of-flight neutron powder diffraction.

C. D. Martin, R. I. Smith, W. G. Marshall, and J. B. Parise (2007)
American Mineralogist 92, 1912-1918
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Compression, thermal expansion, structure, and instability of CaIrO3, the structure model of MgSiO3 post-perovskite.

C. D. Martin, K. W. Chapman, P. J. Chupas, V. Prakapenka, P. L. Lee, S. D. Shastri, and J. B. Parise (2007)
American Mineralogist 92, 1048-1053
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The density and compressibility of KAlSi3O8 liquid to 6.5 GPa.

R. A. Lange (2007)
American Mineralogist 92, 114-123
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The Structure of Silicate Glasses and Melts.

G. S. Henderson, G. Calas, and J. F. Stebbins (2006)
Elements 2, 269-273
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