Formation of Iron-Helium Compounds under High Pressure

• DOI: 10.48550/arxiv.2405.11810
• Publication Date: 2025-02-25
• Authors: Haruki Takezawa; Han Hsu; Kei Hirose; Fumiya Sakai; Suyu Fu; Hitoshi Gomi; Shiro Miwa; Naoya Sakamoto
• Keywords: Condensed Matter - Other Condensed Matter; Condensed Matter - Materials Science; Materials Science (cond-mat.mtrl-sci); FOS: Physical sciences; Other Condensed Matter (cond-mat.other)

We report the formations of fcc and distorted hcp iron-helium compounds with x in FeHex 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 FeHex were still observed by XRD and SIMS measurements. Our first-principles calculations indicate that fcc and hcp FeHex, 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 3He.<br/>44 pages, 23 figures, 5 tables<br/>