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Density of Fe-Ni-C Liquids at High Pressures and Implications for Liquid Cores of Earth and the Moon

Journal Article · · Journal of Geophysical Research. Solid Earth
DOI:https://doi.org/10.1029/2020jb021089· OSTI ID:1774188
 [1];  [2];  [3];  [4];  [5];  [6];  [7];  [8];  [9];  [8]
  1. China Univ. of Geosciences, Wuhan (China); Univ. of Hawaii at Manoa, Honolulu, HI (United States)
  2. Univ. of Hawaii at Manoa, Honolulu, HI (United States); China Univ. of Geosciences, Wuhan (China)
  3. Louisiana State Univ., Baton Rouge, LA (United States)
  4. Univ. of Hawaii at Manoa, Honolulu, HI (United States); Case Western Reserve Univ., Cleveland, OH (United States)
  5. Ehime Univ., Matsuyama (Japan)
  6. Argonne National Lab. (ANL), Argonne, IL (United States). Advanced Photon Source (APS)
  7. Southern Univ. of Science and Technology, Shenzhen (China)
  8. Univ. of Hawaii at Manoa, Honolulu, HI (United States)
  9. Univ. of California, Santa Cruz, CA (United States)
+ Show Author Affiliations
The presence of light elements in the metallic cores of the Earth, the Moon, and other rocky planetary bodies has been widely proposed. Carbon is among the top candidates in light of its high cosmic abundance, siderophile nature, and ubiquity in iron meteorites. It is, however, still controversial whether carbon-rich core compositional models can account for the seismic velocity observations within the Earth and lunar cores. In this paper we report the density and elasticity of Fe90Ni10-3 wt.% C and Fe90Ni10-5 wt.% C liquid alloys using synchrotron-based X-ray absorption experiments and first-principles molecular dynamics simulations. Our results show that alloying of 3 wt.% and 5 wt.% C lowers the density of Fe90Ni10 liquid by ~2.9-3.1% at 2 GPa, and ~3.4-3.6% at 9 GPa. More intriguingly, our experiments and simulations both demonstrate that the bulk moduli of the Fe-Ni-C liquids are similar to or slightly higher than those of Fe-Ni liquids. Thus, the calculated compressional velocity ($$v_p$$) of Fe-Ni-C liquids are higher than that of pure Fe-Ni alloy, promoting carbon as a possible candidate to explain the elevated v p in the Earth's outer core. However, the values and slopes of both density and v p of the studied two Fe-Ni-C liquids do not match the outer core seismic models, suggesting that carbon may not be the sole principal light element in Earth's outer core. The high $$v_p$$ of Fe-Ni-C liquids does not match the presumptive $$v_p$$ of the lunar outer core well, indicating that carbon is less likely to be its dominant light element.
Research Organization:
Argonne National Laboratory (ANL), Argonne, IL (United States). Advanced Photon Source (APS); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Organization:
Japan Society for the Promotion of Science (JSPS); National Natural Science Foundation of China (NSFC); National Science Foundation (NSF); USDOE National Nuclear Security Administration (NNSA); USDOE Office of Science (SC)
Grant/Contract Number:
AC02-05CH11231; AC02-06CH11357
OSTI ID:
1774188
Journal Information:
Journal of Geophysical Research. Solid Earth, Journal Name: Journal of Geophysical Research. Solid Earth Journal Issue: 3 Vol. 126; ISSN 2169-9313
Publisher:
American Geophysical UnionCopyright Statement
Country of Publication:
United States
Language:
English

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Related Subjects

58 GEOSCIENCES
Fe‐Ni‐C liquid
X‐ray absorption
cores of Earth and the Moon
density
first‐principles
molecular dynamics
velocity