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Updated: May 22, 2025

Synthesis and Microdiffraction at Extreme Pressures and Temperatures
Published on: October 7, 2013
Formation of Iron-Helium Compounds under High Pressure
Haruki Takezawa1, Han Hsu2, Kei Hirose1,3
1The University of Tokyo, Department of Earth and Planetary Science, Tokyo 113-0033, Japan.
Abstract:
We report the formation of fcc and distorted hcp iron-helium compounds with x in FeHe_{x} up to 0.13 and 0.48, respectively, based on experiments at 5-54 GPa and ∼1000-2820 K. Upon releasing pressure under room temperature, these fcc and distorted hcp FeHe_{x} were still observed by XRD and SIMS measurements. Our first-principles calculations indicate that fcc and hcp FeHe_{x}, with helium atoms occupying the tetrahedral and trigonal-planar interstitial sites (instead of the octahedral sites), are dynamically stable throughout 0-50 GPa. These results support that the Earth's core can be a large reservoir of primordial ^{3}He.
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