Novel Superconductivity in MetallicSnH4under High Pressure

From first-principles calculations, a high-pressure metallic phase of $\mathrm{Sn}{\mathrm{H}}_4$ with a novel layered structure intercalated by “${\mathrm{H}}_2$” units is revealed. This structure is stable at pressure between 70 and 160 GPa. A remarkable feature of this structure is the presence of soft modes in the phonon band structure induced by Fermi surface nesting and Kohn anomalies that lead to very strong electron-phonon coupling. The application of the Allen-Dynes modified McMillan equation with the calculated electron-phonon coupling parameter $\lambda$ shows that a superconducting critical temperature close to 80 K can be achieved at 120 GPa.