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American Mineralogist

Journal of Earth and Planetary Materials

Ed. by Baker, Don / Xu, Hongwu / Swainson, Ian


IMPACT FACTOR 2017: 2.645

CiteScore 2017: 2.31

SCImago Journal Rank (SJR) 2017: 1.440
Source Normalized Impact per Paper (SNIP) 2017: 1.059

Online
ISSN
1945-3027
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Volume 82, Issue 1-2

Issues

Structure and elasticity of MgO at high pressure

B.B. Karki
  • Department of Physics and Astronomy, University of Edinburgh, Edinburgh, ER9 3JZ Scotland, U.K.
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/ L. Stixrude
  • School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, Georgia 30332-0340, U.S.A.
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/ S.J. Clark
  • Department of Physics and Astronomy, University of Edinburgh, Edinburgh, ER9 3JZ Scotland, U.K.
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/ M.C. Warren
  • Department of Physics and Astronomy, University of Edinburgh, Edinburgh, ER9 3JZ Scotland, U.K.
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/ G.J. Ackland
  • Department of Physics and Astronomy, University of Edinburgh, Edinburgh, ER9 3JZ Scotland, U.K.
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/ J. Crain
  • Department of Physics and Astronomy, University of Edinburgh, Edinburgh, ER9 3JZ Scotland, U.K.
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Published Online: 2015-11-13 | DOI: https://doi.org/10.2138/am-1997-1-207

Abstract

The structural and elastic properties of MgO periclase were studied up to 150 GPa with the first-principles pseudopotential method within the local density approximation. The calculated lattice constant of the B1 phase over the pressure range studied is within 1% of experimental values. The observed B1 phase of MgO was found to be stable up to 450 GPa, precluding the B1-B2 phase transition within the lower mantle. The calculated tran­sition pressure is less than one-half of the previous pseudopotential prediction but is very close to the linearized augmented plane-wave result. All three independent elastic con­stants, c11, c12, and c44, for the B1 phase are calculated from direct computation of stresses generated by small strains. The calculated zero-pressure values of the elastic moduli and wave velocities and their initial pressure dependence are in excellent agreement with ex­periments. MgO was found to be highly anisotropic in its elastic properties, with the magnitude of the anisotropy first decreasing between 0 and 15 GPa and then increasing from 15 to 150 GPa. Longitudinal and shear-wave velocities were found to vary by 23 and 59%, respectively, with propagation direction at 150 GPa. The character of the an­isotropy changes qualitatively with pressure. At zero pressure longitudinal and shear-wave propagations are fastest along [111] and [100], respectively, whereas above 15 GPa, the corresponding fast directions are [100] and [110]. The Cauchy condition was found to be strongly violated in MgO, reflecting the importance of noncentral many-body forces.

About the article

Received: 1996-02-23

Accepted: 1996-10-01

Published Online: 2015-11-13

Published in Print: 1997-01-01


Citation Information: American Mineralogist, Volume 82, Issue 1-2, Pages 51–60, ISSN (Online) 1945-3027, ISSN (Print) 0003-004X, DOI: https://doi.org/10.2138/am-1997-1-207.

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© 2015 by Walter de Gruyter Berlin/Boston.

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