Superconductivity of lithium-doped hydrogen under high pressure

The high-pressure lattice dynamics and superconductivity of newly proposed lithium hydrides (LiH2, LiH6 and LiH8) have been extensively studied using density functional theory. The application of the Allen-Dynes modified McMillan equation and electron-phonon coupling calculations show that LiH6 and LiH8 are superconductors with critical temperatures (T-c) of 38 K at 150 GPa for LiH6 and 31 K at 100 GPa for LiH8, while LiH2 is not a superconductor. The T-c of LiH6 increases rapidly with pressure and reaches 82 K at 300 GPa due to enhancement of the electron-phonon coupling and the increased density of states at the Fermi level, while the T-c of LiH8 remains almost constant.