Superconductivity in CeBeH${}_8$ and CeBH${}_8$ at moderate pressures

Abstract

High-pressure structural searches of superhydrides CeBeH${}_8$ and CeBH${}_8$ were performed under ambient pressure up to 300 GPa. We identify $Fm\overline{3}m$-CeBeH${}_8$ with a superconducting transition temperature $T_c$ of 56 K at 10 GPa. Two more phases with spacegroup $R\overline{3}m$ and $C2/m$, were investigated within the increasing pressures. CeBH${}_8$ shows a similar phase transition process as CeBeH${}_8$ but with higher transition pressures and higher $T_c$. $Fm\overline{3}m$-CeBH${}_8$ is predicted to be superconducting above 120 GPa with a maximum $T_c$ of 118 K at 150 GPa. $R\overline{3}m$-CeBH${}_8$ and $C2/m$-CeBH${}_8$ are dynamically stable above 120 GPa and 100 GPa, respectively. The maximum $T_c$ is 123 K at 195 GPa for $R\overline{3}m$-CeBH${}_8$, and 115 K at 350 GPa for $C2/m$-CeBH${}_8$. Our work enriches the family of ternary hydrides and may provide a useful guideline for further search for superconducting hydrides at low and moderate pressures.