Prediction of Stability and Superconductivity in Ternary Hydride Li₂BeH₆: Two Metastable Superconductors

Inspired by a remarkably high-temperature superconductivity (T-c similar to 473 K) obtained from ternary lithium magnesium hydride and considering the relatively close electronegativity of the elements magnesium and beryllium, similar superconductivity could also appear in ternary lithium beryllium hydride. Here, we investigate the structural stabilities and superconducting properties of Li2BeH6 at 50-400 GPa based on the first-principles calculation and the CALYPSO structure prediction method. The calculated results show that the ground state of Li2BeH6 is maintained as the Pbam phase at 50-400 GPa. In addition, a phase transition from semiconductor to metal occurs at about 300 GPa, and the superconducting transition temperature of 19 K at 350 GPa is predicted. More importantly, two highly symmetric metastable phases I4/mmm and Fm3m are found in Li2BeH6, which can be synthesized in an experiment by analyzing their decomposition routes. Electron-phonon coupling analysis reveals that I4/mmm and Fm3m might be potential high temperature superconductors with a T-c of 134 and 149 K at 150 and 100 GPa respectively, which slightly higher than 98 K at 100 GPa in Li2BH6. This excellent superconductivity may be attributed to the BeH6 octahedral structure with a laminar distribution in I4/mmm and Fm3m. Our studies will provide some new thoughts for further in-depth exploration of ternary hydrogen-rich compounds with superior superconducting properties.