Prediction for high superconducting ternary hydrides below megabar pressure.

The recent findings of high-temperature hydrides ushered a new era of superconductivity research under high pressure. However, the stable pressure for these remarkable hydrides remains extremely high. In this work, we performed the extensive simulations on a series of hydrides with the prototype structure of UH 8 and UH 7 . Our results indicate several compounds possess superconducting critical temperature ( T c ) above liquid nitrogen temperature below 100 GPa, such as CeBeH 8 and ThBeH 8 that are dynamical stable with a T c of 201 K at 30 GPa and a T c of 98 K at 10 GPa, respectively. Further formation enthalpy calculations suggest that thermodynamical stable pressure of CeBeH 8 and ThBeH 8 compounds is above 50 GPa and 88 GPa with respect to binary compounds and solid elements. Moreover, we also found that ThBeH 7 could be dynamically stable down to 20 GPa with a T c of 70 K. Our further simulations suggested this newly predicted ThBeH 7 is thermodynamically stable above pressure of 33 GPa with respect to binary compounds and solid elements. The present results shed light on future design and discovery of high-temperature superconductor at moderate pressure.