TY - JOUR
T1 - Hydrogen and Silicon Effects on Hexagonal Close Packed Fe Alloys at High Pressures
T2 - Implications for the Composition of Earth's Inner Core
AU - Fu, Suyu
AU - Chariton, Stella
AU - Prakapenka, Vitali B.
AU - Shim, Sang Heon
N1 - Funding Information:
We thank an anonymous reviewer and Dr. Y. Fei for questions and comments which improved this paper. This work is supported by NSF-Astronomical Science (AST200567 and AST2108129) and NSF-Earth Science (EAR1921298). The authors acknowledge the support of GeoSoilEnviroCARS (University of Chicago, Sector 13) for synchrotron experiments. GeoSoilEnviroCARS was supported by the National Science Foundation—Earth Sciences (EAR-1634415). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
Funding Information:
We thank an anonymous reviewer and Dr. Y. Fei for questions and comments which improved this paper. This work is supported by NSF‐Astronomical Science (AST200567 and AST2108129) and NSF‐Earth Science (EAR1921298). The authors acknowledge the support of GeoSoilEnviroCARS (University of Chicago, Sector 13) for synchrotron experiments. GeoSoilEnviroCARS was supported by the National Science Foundation—Earth Sciences (EAR‐1634415). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE‐AC02‐06CH11357.
Publisher Copyright:
© 2023. American Geophysical Union. All Rights Reserved.
PY - 2023/4
Y1 - 2023/4
N2 - Hexagonal close-packed (hcp) structured Fe-Ni alloy is believed to be the dominant phase in the Earth's inner core. This phase is expected to contain 4%–5% light elements, such as Si and H. While the effects of individual light element candidates on the equation of state (EoS) of the hcp Fe metal have been studied, their combined effects remain largely unexplored. In this study, we report the equations of state for two hcp-structured Fe-Si-H alloys, namely Fe0.83Si0.17H0.07 and Fe0.83Si0.17H0.46, using synchrotron X-ray diffraction measurements up to 125 GPa at 300 K. These alloys were synthesized by cold compression of Fe-9wt%Si in either pure H2 or Ar-H2 mixture medium in diamond-anvil cells. The volume increase caused by a H atom in hcp Fe-Si-H alloys is approximately eight times greater than that by a Si atom. We used the improved data set to develop a composition-dependent EoS that covers a wide range of compositions. Our calculated density and bulk sound velocity of hcp Fe-Si-H alloys suggest a large trade-off between Si and H contents in fitting the seismic properties of the inner core. Combining our new EoS with geophysical and geochemical constraints, we propose 1.6–3 wt% Si and 0.15–0.6 wt% H in the Earth's inner core.
AB - Hexagonal close-packed (hcp) structured Fe-Ni alloy is believed to be the dominant phase in the Earth's inner core. This phase is expected to contain 4%–5% light elements, such as Si and H. While the effects of individual light element candidates on the equation of state (EoS) of the hcp Fe metal have been studied, their combined effects remain largely unexplored. In this study, we report the equations of state for two hcp-structured Fe-Si-H alloys, namely Fe0.83Si0.17H0.07 and Fe0.83Si0.17H0.46, using synchrotron X-ray diffraction measurements up to 125 GPa at 300 K. These alloys were synthesized by cold compression of Fe-9wt%Si in either pure H2 or Ar-H2 mixture medium in diamond-anvil cells. The volume increase caused by a H atom in hcp Fe-Si-H alloys is approximately eight times greater than that by a Si atom. We used the improved data set to develop a composition-dependent EoS that covers a wide range of compositions. Our calculated density and bulk sound velocity of hcp Fe-Si-H alloys suggest a large trade-off between Si and H contents in fitting the seismic properties of the inner core. Combining our new EoS with geophysical and geochemical constraints, we propose 1.6–3 wt% Si and 0.15–0.6 wt% H in the Earth's inner core.
UR - http://www.scopus.com/inward/record.url?scp=85158921186&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85158921186&partnerID=8YFLogxK
U2 - 10.1029/2022JB026016
DO - 10.1029/2022JB026016
M3 - Article
AN - SCOPUS:85158921186
SN - 2169-9313
VL - 128
JO - Journal of Geophysical Research: Solid Earth
JF - Journal of Geophysical Research: Solid Earth
IS - 4
M1 - e2022JB026016
ER -