Crystal Structure and Physical Properties of Sr₂He Compound under High Pressure

By combining first-principles calculations under the framework of density functional theory (DFT) and the CALYPSO crystal structure prediction method, the structural stability of the inert element helium (He) and alkaline-earth metals under high-pressure conditions has been systematically investigated. The calculations reveal that among the alkaline-earth metals, strontium (Sr) forms compounds with He exhibiting relatively low energy values. Consequently, the crystal structure of Sr₂He at 400 GPa was predicted. Electron localization function (ELF) and density of states (DOS) analyses show no tendency for covalent bond formation between Sr and He atoms. Furthermore, Bader charge analysis reveals ionic bonding between Sr and He atoms, with charge transfer occurring from He to Sr. These results provide key insights into the bonding mechanism of Sr₂He. This study elucidates the crystal structure, bonding nature, and electronic properties of Sr₂He, offering theoretical support for understanding the stability and physical properties of such metastable materials and providing important guidance for their experimental synthesis.