Superconducting high pressure phase of GeH4

Through ab initio evolutionary methodology, we reveal a high-pressure metallic structure of GeH4 with C2/c symmetry. This structure contains novel “H2” units. Enthalpy calculations suggest a wide decomposition (Ge+H2) pressure range of 0—196 GPa, above which the C2/c structure is stable. Perturbative linear response calculations for C2/c at 220 GPa predict a large electron-phonon coupling parameter of 1.12 and a resulting superconducting critical temperature of 64 K.