Superconducting H chain in gallium hydrides at high pressure.

Pressure-stabilized hydrides have potential as an outstanding reservoir for high-temperature () superconductors. We undertook a systematic study of crystal structures and superconducting properties of gallium hydrides using an advanced structure-search method together with first-principles calculations. We identified an unconventional stoichiometric GaH gallium hydride that is thermodynamically stable at pressures above 247 GPa.