Equation of state of iron-silicon alloys to megabar pressure

N. Hirao, E. Ohtani, T. Kondo, T. Kikegawa

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39 Citations (Scopus)


The stability and pressure-volume equation of state of iron-silicon alloys, Fe-8.7 wt% Si and Fe-17.8 wt% Si, have been investigated using diamond-anvil cell techniques up to 196 and 124 GPa, respectively. Angular-dispersive X-ray diffractions of iron-silicon alloys were measured at room temperature using monochromatic synchrotron radiation and an imaging plate (IP). A bcc-Fe-8.7 wt% Si transformed to hcp structure at around 16∼36 GPa. The high-pressure phase of Fe-8.7 wt% Si with hexagonal close-packed (hcp) structure was found to be stable up to 196 GPa and no phase transition of bcc-Fe-17.8 wt% Si was observed up to 124 GPa. The pressure-volume data were fitted to a third-order Birch-Murnaghan equation of state (BM EOS) with zero-pressure parameters: V0=22.2(8) Å3, K0 = 198(9) GPa, and K'0=4.7(3) for hcp-Fe-8.7 wt% Si and V0 = 179.41(45) Å3, K'0=207(15) GPa and K'0=5.1(6) for Fe-17.8 wt% Si. The density and bulk sound velocity of hcp-Fe-8.7 wt% Si indicate that the inner core could contain 3-5 wt% Si.

Original languageEnglish
Pages (from-to)329-336
Number of pages8
JournalPhysics and Chemistry of Minerals
Issue number6
Publication statusPublished - 2004 Jul


  • Equation of state
  • High pressure
  • Iron-silicon alloys
  • X-ray diffraction

ASJC Scopus subject areas

  • Materials Science(all)
  • Geochemistry and Petrology


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