Superconducting H7 chain in gallium hydrides at high pressure

Abstract

Pressure-stabilized hydrides have potential as an outstanding reservoir for high-temperature (T_c) 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 GaH₇ gallium hydride that is thermodynamically stable at pressures above 247 GPa. Interestingly, the H atoms are clustered to form a unique H₇ chain intercalating the Ga framework. Further calculations show a high estimated T_c above 100 K at 200–300 GPa for GaH₇, closely related to the strong coupling between electrons of Ga and H atoms, and phonon vibrations of H₇ chains. Our work provides an example of exploration for diverse superconducting hydrogen motifs under high pressure, and may stimulate further experimental syntheses.