First-principles study on stability and superconductivity of ternary hydride LaYH x (x = 2, 3, 6 and 8)

Recent studies have shown that the La- and Y-hydrides can exhibit significant superconducting properties under high pressures. In this paper, we investigate the stability, electronic and superconducting properties of LaYH x ( x = 2, 3, 6 and 8) under 0–200 GPa. It is found that LaYH 2 stabilizes in the C 2/ m phase at ambient pressure, and transforms to the Pmmn phase at 67 GPa. LaYH 3 stabilizes in the C 2/ m phase at ambient pressure, and undergoes phase transitions of C 2/ m → P 2 1 / m → R 3 m at 12 GPa and 87 GPa, respectively. LaYH 6 stabilizes in the P 4 3 2 1 2 phase at ambient pressure, and undergoes phase transitions of P 4 3 2 1 2 → P4/ mmm → Cmcm at 28 GPa and 79 GPa, respectively. LaYH 8 stabilizes in the Imma phase at 60 GPa and transforms to the P 4/ mmm phase at 117 GPa. Calculations of the electronic band structures show that the P 4/ mmm -LaYH 8 and all phases of LaYH 2 and LaYH 3 exhibit metallic character. For the metallic phases, we then study their superconducting properties. The calculated superconducting transition temperatures ( T c ) are 0.47 K for C 2/ m -LaYH 2 at 0 GPa, 0 K for C 2/ m -LaYH 3 at 0 GPa, and 55.51 K for P 4/ mmm -LaYH 8 at 50 GPa.