Ab initio studies of copper hydrides under high pressure

The crystal structure, electronic structure, and superconductivity of copper hydrides at high pressure have been studied by ab initio calculation. Consistent with experimental report, results show that the predicted stoichiometry Cu2H with the P-3m1 space group is stable above 16.8 GPa. The stoichiometry of CuH with the Fm-3m space group is predicted to be synthesized above 30 GPa, but it is metastable and dynamical instable up to 120 GPa. The electronic band calculations reveal that Cu2H is a good metal at a stable pressure range, whereas CuH is an insulator. Moreover, the other hydrogen-rich compounds CuH2 and CuH3 are thermodynamically and dynamically unstable, respectively. The calculated superconducting transition temperature (T-c) of Cu2H at 40 GPa is 0.028 K by using the Allen-Dynes modified McMillan equation.