Post-stishovite transition in hydrous aluminous SiO2

Koichiro Umemoto, Katsuyuki Kawamura, Kei Hirose, Renata M. Wentzcovitch

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11 Citations (Scopus)

Abstract

Lakshtanov et al. (2007) showed that incorporation of aluminum and some water into SiO2 significantly reduces the post-stishovite transition pressure in SiO2. This discovery suggested that the ferroelastic post-stishovite transition in subducted MORB crust could be the source of reflectors/scatterers with low shear velocities observed in the mid to upper lower mantle. A few years later, a similar effect was observed in anhydrous Al-bearing silica. In this paper, we show by first principles static calculations and by molecular dynamics using inter-atomic potentials that hydrogen bonds and hydrogen mobility play a crucial role in lowering the post-stishovite transition pressure. A cooperative redistribution of hydrogen atoms is the main mechanism responsible for the transition pressure reduction in hydrous aluminous stishovite. The effect is enhanced by increasing hydrogen concentration. This perspective suggests a potential relationship between the depth of seismic scatterers and the water content in stishovite.

Original languageEnglish
Pages (from-to)18-26
Number of pages9
JournalPhysics of the Earth and Planetary Interiors
Volume255
DOIs
Publication statusPublished - Jun 1 2016

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Keywords

  • First principles
  • Hydrous aluminous SiO
  • Molecular dynamics
  • Post-stishovite transition

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science
  • Physics and Astronomy (miscellaneous)
  • Astronomy and Astrophysics

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