Pressure-induced novel phases with the high-Tc superconductivity in zirconium dihydride

The unprecedented structures in hydrides could be uncovered under high pressure, which probably possess unusual properties, such as high-Tc superconductivity. Here, the structural transition of ZrH2 at 0-500 GPa are comprehensively explored by using the evolutionary algorithm in the universal structure predictor combined with first-principles calculations. Three new phases are found: Pnma-ZrH2, P-3m1-ZrH2 and R-3m-ZrH2, with dynamic stability. Moreover, the sequence of phases of ZrH2 under pressure is I4/mmm -> P4/nmm -> Pnma -> P3m1 -> R-3m with the zero-point energy effects. Structural feature, electronic properties, bonding characters and superconductivity of all the ZrH2 are analyzed in detail. More importantly, the superconducting critical temperature Tc values for P-3m1 at 440 GPa and R-3m at 500 GPa are 17.70-20.14 K and 26.68-30.03 K, respectively, which stems from the strong electron-phonon coupling.