First-Principles Study of the Crystal Structure and Elastic Properties of FeO₂H₂He under High Pressure

The composition and seismic anomalies of the deep Earth serve as key research topics, and the high ³He/⁴He ratio in ocean island basalts indicates the presence of the primordial helium reservoir in the Earth’s deep interior. However, our understanding of stable helium-bearing compounds in the deep Earth is still limited. This study systematically calculated the crystal structure and elastic properties of FeO₂H₂He at 30–150 GPa using first principles methods based on density functional theory. The static calculation results of phonon dispersion and elastic constants indicate that the R3m cubic crystal structure of FeO₂H₂He exhibits excellent local dynamic stability and mechanical stability within the studied pressure range. Poisson’s ratio and Pugh ratio analyses consistently show that FeO₂H₂He exhibits a ductile state throughout the investigated pressure range. The comprehensive characteristics of density and wave velocity reveal that FeO₂H₂He could potentially serve as one of the helium-bearing components near the core-mantle boundary, and may represent a potential mineral component for explaining the wave velocity anomalies observed in ultra-low velocity zones (ULVZs). This research enriches our understanding of the core-mantle boundary composition and provides new mineralogical constraints on the occurrence and distribution of helium in the deep Earth.