Prediction of high-temperature superconductivity in hexagonal and rhombohedral phases of metallic hydrogen

Under extreme pressure, hydrogen is predicted to transform from a low-pressure molecular solid into an atomic solid. Several candidate structures for the atomic solid are studied as candidates for superconductivity. In particular, the 9R (α-SM) structure is found to be stable with a predicted transition temperature ${\mathit{T}}_{\mathit{c}}$=140–170 K. Results for hexagonal phases are also discussed.