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Title: 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 ten 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-7wt.%Si adopts the hexagonal close packed (hcp) structure over the measured pressure range, whereas Fe-15wt.%Si is observed in a body-centered cubic (bcc) 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 such planets.
 [1] ;  [2] ;  [2] ;  [2] ;  [2] ;  [3] ;  [2] ;  [2] ;  [4]
  1. Princeton Univ., Princeton, NJ (United States); Johns Hopkins Univ., Baltimore, MD (United States)
  2. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
  3. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  4. Princeton Univ., Princeton, NJ (United States)
Publication Date:
Grant/Contract Number:
NA0002720; NA0003611
Accepted Manuscript
Journal Name:
Science Advances
Additional Journal Information:
Journal Volume: 4; Journal Issue: 4; Journal ID: ISSN 2375-2548
Research Org:
Princeton Univ., NJ (United States)
Sponsoring Org:
USDOE National Nuclear Security Administration (NNSA), Office of Defense Programs (DP) (NA-10)
Contributing Orgs:
Laboratory for Laser Energetics
Country of Publication:
United States
58 GEOSCIENCES; high pressure; exoplanets; iron-silicon alloy; ramp compression
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1439048