Abstract
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, K0=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.
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Acknowledgments
This work is supported by a grant-in-aid for the Scientific Research of Priority Area (no. 12126201) and the Scientific Research (S) (no. 14102009) of Ministry of Education, Culture, Sport, Science, and Technology of Japanese Government to E. Ohtani. X-ray diffraction experiments were performed under the approval of the Photon Factory Program Advisory Committee (proposal numbers: 01G059 and 02G055). We thank L.S. Dubrovinsky and F. Guyot for their careful reviews and comments on the manuscript.
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Hirao, N., Ohtani, E., Kondo, T. et al. Equation of state of iron–silicon alloys to megabar pressure. Phys Chem Minerals 31, 329–336 (2004). https://doi.org/10.1007/s00269-004-0387-x
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DOI: https://doi.org/10.1007/s00269-004-0387-x