High-Temperature Superconductivity in Th-H System at Pressure Conditions

New stable thorium decahydride $Fm\bar{3}m$-$Th{H}_{10}$, a record high-temperature superconductor with $T_C$ up to 241 K ($-{32}^{\circ }C$), critical field $H_C$ up to 71T and superconducting gap ${\mathrm{\Delta }}_0$ = 52 meV at 80-100 GPa was predicted by evolutionary algorithm USPEX. Another phase $P{2}_{1}c$-$Th{H}_7$ was found to be a high-temperature superconductor with $T_C$ of 65 K. Analysis of superconducting state was performed within Eliashberg formalism and the dependencies of $H_C(T)$, ${\mathrm{\Delta }}_0(T)$, $T_C(P)$ together with jump in the specific heat at critical temperature were calculated. Several other new thorium hydrides were predicted to be stable under pressure including $Th{H}_3$, $T{h}_3{H}_{10}$, $Th{H}_4$, $Th{H}_6$. 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-Ac). Thorium - is the next member in Mg-Ca-Sc-Y-La-Ac family of elements forming high-$T_C$ superconducting hydrides.