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Elastic Properties of hcp ‐Structured Fe‐C and Fe‐C‐H Alloys at High Pressures: Implications on Earth's Core

Year: 2025

Type: article

Abstract: Carbon and hydrogen are both potential light elements in the Earth's core. However, the stability and elastic properties of Fe‐C‐H ternary alloy under high pressure have rarely been explored. In this study, we synthesized a new hcp ‐structured Fe‐C‐H alloy (FeC 0.065 H 1.05 ) at high pressure using the laser‐heated diamond anvil cell. Hydrogen incorporation significantly expands the volume and decreases the bulk modulus of hcp Fe and Fe‐C alloy (FeC 0.065 ). It also elevates the c / a ratio, potentially explaining the anisotropy of the Earth's inner core. Furthermore, the incorporation of carbon and hydrogen considerably decreases the density of hcp Fe. 0.3–0.7 wt.% H and 0.2–0.5 wt.% C in Fe alloys could account for the observed density deficit of the inner core with 7,000–5,000 K inner core boundary temperature. A tradeoff relationship was established that the effect of 4 wt.% carbon is equivalent to 1 wt.% hydrogen on the density of inner core.

Source: Geophysical Research Letters

DOI: 10.1029/2025gl115276

Authors: Xiaojing Lai, Feng Zhu, Jing Yang, Stella Chariton, Vitali B. Prakapenka, Xiang Wu, Bin Chen

Institutions: University of Hawaiʻi at Mānoa, China University of Geosciences, State Key Laboratory of Geological Processes and Mineral Resources, Carnegie Institution for Science, Earth and Planets Laboratory, University of Chicago

Language: English

Topic: High-pressure geophysics and materials

Subfield: Geophysics

Field: Earth and Planetary Sciences

Domain: Physical Sciences

Open Access status: gold

Estimated APC paid: $3,190

Funders: National Science Foundation, U.S. Department of Energy, National Natural Science Foundation of China, Office of Science, Argonne National Laboratory

Awards: G102163711, GeoSoilEnviroCARS: A National Resource for Earth, Planetary, Soil and Environmental Science Research at the APS, G107546177, G1092076044, Laboratory Technician Support: Experimental Mineral Physics and Petrology Facilities at the University of Hawaii at Manoa, G1313983767, G1511624953, GEOSOILENVIROCARS: A NATIONAL RESOURCE FOR EARTH, PLANETARY, SOIL AND ENVIRONMENTAL SCIENCE RESEARCH AT THE ADVANCED PHOTON SOURCE, G1664757510, G1772725214, G1996433053, G2025663771, G222768804, G2287611682, G262962599, G3075337988, CAREER: Elasticity and Lattice Dynamics of Iron Alloys under Earth's Core Conditions, GEO CARS: A NATIONAL RESOURCE FOR EARTH, PLANETARY AND ENVIRONMENTAL SCIENCE RESEARCH AT THE ADVANCED PHOTON SOURCE, G498139845, G513797252, G6254355288, G6848031779, G6918803902, G8589042016, G880751848, GEOSOILENVIROCARS: A NATIONAL RESOURCE FOR EARTH, PLANETARY, SOIL AND ENVIRONMENTAL SCIENCE RESEARCH AT THE ADVANCED PHOTON SOURCE, G969889393, G993149817

OpenAlex ID: W4413794577

FWCI: 0.623

Cites: 45

Cited by: 1

Related to: 10