Equation of state of pure iron and Fe0.9Ni0.1 alloy up to 3Mbar

Takeshi Sakai, Suguru Takahashi, Naoya Nishitani, Izumi Mashino, Eiji Ohtani, Naohisa Hirao

Research output: Contribution to journalArticlepeer-review

46 Citations (Scopus)


Pure iron and Fe0.9Ni0.1 alloy were compressed to a pressure of 279GPa and 272GPa, respectively. The compression data sets were fitted using the third order Birch-Murnaghan equation of state based on six different pressure scales. Our result shows the nickel increase the density and the c/a ratio, decrease the bulk modulus. The high temperature data obtained the thermal equation of state parameters. At high temperature, although the nickel effect on density slightly decrease due to the a little larger thermal expansion, the bulk modulus difference increase to 7.3-7.8% at 329GPa and 5000K. Nickel effects on elasticity might be important at multimegabar pressure and especially high temperature such as the inner core condition. The core density deficit was estimated to be 3.5(1)-5.3(1)% for pure iron and 4.7(1)-6.5(2)% for Fe0.9Ni0.1 alloy if the temperature at the inner core boundary is 5000K.

Original languageEnglish
Pages (from-to)114-126
Number of pages13
JournalPhysics of the Earth and Planetary Interiors
Publication statusPublished - Mar 2014
Externally publishedYes


  • Bulk modulus
  • Density
  • Equation of state
  • Fe-Ni alloy
  • The inner core

ASJC Scopus subject areas

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


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