Phase diagrams and superconductivity of ternary Ca-Al-H compounds under high pressure

Ming Xu; Defang Duan; Wendi Zhao; Decheng An; Hao Song; Tian Cui

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arXiv · 2305.11678

Phase diagrams and superconductivity of ternary Ca-Al-H compounds under high pressure

Ming Xu·Defang Duan·Wendi Zhao·Decheng An·Hao Song·Tian Cui

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Abstract

The search for high-temperature superconductors in hydrides under high pressure has always been a research hotspot. Hydrogen-based superconductors offer an avenue to achieve the long-sought goal of superconductivity at room temperature. We systematically explore the high-pressure phase diagram, electronic properties, lattice dynamics and superconductivity of the ternary Ca-Al-H system using ab initio methods. We found two stable ternary hydrides at 50 GPa: Cmcm-CaAlH5 and Pnnm-CaAl2H8, which both are semiconductors. At 200 GPa, a new phase of P21/m-CaAlH5, P4/mmm-CaAlH7 and a metastable compound Immm-Ca2AlH12 were found. Furthermore, P4/mmm-CaAlH7 has obvious phonon softening of high frequency vibrations along the Z-A direction, point A and point X, which improves the strength of electron-phonon coupling. Therefore, a superconducting transition temperature Tc of 71 K is generated at 50 GPa. In addition, the thermodynamic metastable Immm-Ca2AlH12 exhibits a superconducting transition temperature of 118 K at 250 GPa. These results are very useful for the experimental searching of new high-Tc superconductors in ternary hydrides.

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Ming Xu, Defang Duan, Wendi Zhao, Decheng An, Hao Song, Tian Cui. 2023-05-19. Phase diagrams and superconductivity of ternary Ca-Al-H compounds under high pressure. https://arxiv.org/abs/2305.11678

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