Theoretical study on the Y-Ba-H hydrides at high pressure

Highlights: • The phases of YBaH₈ appear difference due to the different arrangement of H atoms. • We explored its synthesis path of BaH₂ + YH₆ → YBaH₈. • The properties of YBaH₈ were discussed compared with BaH₂. • The T_c of P4/mmm-YBaH₈ was predicted to be 49.6 K at 50 GPa. It has been a hot issue to search for hydrides at high pressure with high superconducting transition temperature (T_c). In this work, we studied YBaH_n (n = 2∼12) at 50 - 200 GPa and found that most of YBaH₂₋₁₂ are thermodynamically stable with respect to the elementary YBa and H systems at this pressure range. The most stable phases of YBaH₄, YBaH₅ and YBaH₈ from genetic algorithm (GA) search have C2/m, P3m1 and P4/mmm symmetries at 50 GPa, and P6/mmm, R3m and P4/mmm at 150 GPa, respectively. The P4/mmm-YBaH₈ was suggested to be formed by BaH₂ + YH₆ → YBaH₈. In addition, the electric properties, phonon spectra and the superconductivity of the YBaH₈ and BaH₂ were calculated and discussed. The T_c of P4/mmm-YBaH₈ was predicted to be 49.6 K at 50 GPa and 89.4 K at 150 GPa.