Phase stability and compression study of (Fe0.89,Ni0.11)3S up to pressure of the Earth's core

Takeshi Sakai, Eiji Ohtani, Hidenori Terasaki, Seiji Kamada, Naohisa Hirao, Masaaki Miyahara, Masahiko Nishijima

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

An in situ synchrotron powder X-ray diffraction study on (Fe 0.89,Ni0.11)3S was conducted up to 141 GPa and 1590 K. (Fe0.89,Ni0.11)3S has a tetragonal structure, which is the same structure as Ni-free Fe3S. Fitting a third-order Birch-Murnaghan equation of state to data at ambient temperature yielded a bulk modulus of K0 = 138.1(7.2) GPa and its pressure derivative K'0 = 4.5(3) with a zero pressure volume V0 = 375.67(4) Å3. The density of (Fe0.89,Ni 0.11)3S under the core-mantle boundary condition is 1.7% greater than that of Fe3S. The axial ratio (c/a) of (Fe0.89,Ni 0.11)3S decreases with increasing pressure. The addition of nickel to Fe3S leads to a softening of the c-axis. Assuming that the nickel content of the outer core is about 5 at%, we estimated 12.3-20.8 at% sulfur in the outer core for the given 6-10% density deficit between the outer core and pure iron at 136 GPa.

Original languageEnglish
Pages (from-to)1490-1494
Number of pages5
JournalAmerican Mineralogist
Volume96
Issue number10
DOIs
Publication statusPublished - Oct 2011
Externally publishedYes

Keywords

  • Core-mantle boundary
  • Earth's core
  • Equation of state
  • Fe-FeS system
  • Laser-heated diamond-anvil cell
  • Phase relation

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

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