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Crystal structure and equation of state of Fe-Si alloys at super-Earth core conditions

Author(s): Wicks, June K; Smith, Raymond F; Fratanduono, Dayne E; Coppari, Federica; Kraus, Richard G; et al

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Abstract: The high-pressure behavior of Fe alloys governs the interior structure and dynamics of super-Earths, rocky extrasolar planets that could be as much as 10 times more massive than Earth. In experiments reaching up to 1300 GPa, we combine laser-driven dynamic ramp compression with in situ x-ray diffraction to study the effect of composition on the crystal structure and density of Fe-Si alloys, a potential constituent of super-Earth cores. We find that Fe-Si alloy with 7 weight % (wt %) Si adopts the hexagonal close-packed structure over the measured pressure range, whereas Fe-15wt%Si is observed in a body-centered cubic structure. This study represents the first experimental determination of the density and crystal structure of Fe-Si alloys at pressures corresponding to the center of a ~3–Earth mass terrestrial planet. Our results allow for direct determination of the effects of light elements on core radius, density, and pressures for these planets.
Publication Date: 25-Apr-2018
Citation: Wicks, June K., Raymond F. Smith, Dayne E. Fratanduono, Federica Coppari, Richard G. Kraus, Matthew G. Newman, J. Ryan Rygg, Jon H. Eggert, and Thomas S. Duffy. "Crystal structure and equation of state of Fe-Si alloys at super-Earth core conditions." Science advances 4, no. 4 (2018): eaao5864. doi:10.1126/sciadv.aao5864.
DOI: doi:10.1126/sciadv.aao5864
EISSN: 2375-2548
Pages: eaao5864
Language: eng
Type of Material: Journal Article
Journal/Proceeding Title: Science Advances
Version: Final published version. This is an open access article.

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