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

New stable phase thorium decahydride Fm (3) over barm-ThH10, a high-temperature superconductor with T-C up to 241 K (-32 degrees C), critical field H-C up to 71 T, and superconducting gap Delta(0) of 52 meV at 80-100 GPa, is predicted by evolutionary algorithm USPEX. Another phase, P2(1)/c-ThH7, is found to be a superconductor with T-C of 62 K. Analysis of the superconducting state was performed within Eliashberg formalism, and H-C(T), Delta(T), and T-C(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 s(2)d(2) electronic configuration) forms high-T-C polyhydrides similar to those formed by s(2)d(1) metals (Y-La-A(C)). Thorium belongs to the Mg-Ca-Sc-Y-La-Ac family of elements forming high-T-C superconducting hydrides.