Metal-Element-Incorporation Induced Superconducting Hydrogen Clathrate Structure at High Pressure

The recent observation of high critical temperature T_\rm c in lanthanum and Yttrium hydrides confirms the key role of hydrogen cage (H-cage) in determining high superconductivity. Here, we present a new class of metastable H_12 clathrate structures based on the icosahedral cI24-Na that can be stabilized by incorporation of metal elements. Analysis shows that the charge transfer from metal atoms to H atoms contributes to forming the H_12 clathrate. Nine dynamically stable structures are identified to exhibit superconductivity, and a maximum T_\rm c of 28 K is found in voids-doped Mo_6H_24. Calculations reveal that the low T_\rm c is attributed to the weak interaction between H atoms in each cage due to the long H–H distance. The current results provide a possible route to design H-cage containing superconductors.