Journal
AMERICAN MINERALOGIST
Volume 105, Issue 6, Pages 917-921Publisher
MINERALOGICAL SOC AMER
DOI: 10.2138/am-2020-7153
Keywords
FeH; fcc structure; Earth's core; X-ray diffraction; ab initio calculation
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Funding
- JSPS Kakenhi [17K05627]
- Grants-in-Aid for Scientific Research [17K05627] Funding Source: KAKEN
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We examined the crystal structure of FeHX (X similar to 1) (FeH hereafter) at high pressure and temperature by X-ray diffraction up to 137 GPa. Results show that FeH adopts a face-centered cubic (fcc) structure at pressures of 43 to 137 GPa and temperatures of similar to 1000 to 2000 K. Our study revises a phase diagram of stoichiometric FeH in which fcc has a wider-than-expected stability field at high pressure and temperature. Based on our findings, the FeH end-member of the Fe-FeH system is expected to be stable in the fcc structure at the P-T conditions of the Earth's core, rather than in the double-hexagonal close packed (dhcp) structure as previously reported. We compared the experimentally determined unit-cell volumes of FeH with those from ab initio calculations. Additionally, we observed a change in compressibility at similar to 60 GPa, which could be attributed to a magnetic transition-an interpretation supported by our ab initio computations.
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