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

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 diffrac...

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Bibliographic Details
Published in:Science advances 2018-04, Vol.4 (4), p.eaao5864-eaao5864
Main Authors: Wicks, June K, Smith, Raymond F, Fratanduono, Dayne E, Coppari, Federica, Kraus, Richard G, Newman, Matthew G, Rygg, J Ryan, Eggert, Jon H, Duffy, Thomas S
Format: Article
Language:English
Subjects:
exoplanets
GEOSCIENCES
high pressure
iron-silicon alloy
Physics
Planetary Science
ramp compression
SciAdv r-articles
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Summary: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.
ISSN:2375-2548
2375-2548
DOI:10.1126/sciadv.aao5864