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

It has been a hot issue to search for hydrides at high pressure with high superconducting transition temperature (Tc). In this work, we studied YBaHn (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 Tc of P4/mmm-YBaH8 was predicted to be 49.6 K at 50 GPa and 89.4 K at 150 GPa.