High-Temperature Superconductivity in a Th-H System under Pressure Conditions.

New stable phase thorium decahydride Fm3̅ m-ThH10, a high-temperature superconductor with TC up to 241 K (-32 °C), critical field HC up to 71 T, and superconducting gap Δ0 of 52 meV at 80-100 GPa, is predicted by evolutionary algorithm USPEX. Another phase, P21/ c-ThH7, is found to be a superconductor with TC of 62 K. Analysis of the superconducting state was performed within Eliashberg formalism, and HC( T), Δ( T), and TC( P) functions with a jump in the specific heat at critical temperature were calculated. Several other new thorium hydrides were predicted to be stable under pressure, including ThH3, Th3H10, ThH4, and ThH6. Thorium (which has s2 d2 electronic configuration) forms high- TC polyhydrides similar to those formed by s2 d1 metals (Y-La-Ac). Thorium belongs to the Mg-Ca-Sc-Y-La-Ac family of elements forming high- TC superconducting hydrides.