Predicted hot superconductivity in LaSc 2 H 24 under pressure.

The recent theory-driven discovery of a class of clathrate hydrides (e.g., CaH 6 , YH 6 , YH 9 , and LaH 10 ) with superconducting critical temperatures ( T c ) well above 200 K has opened the prospects for "hot" superconductivity above room temperature under pressure. Recent efforts focus on the search for superconductors among ternary hydrides that accommodate more diverse material types and configurations compared to binary hydrides. Through extensive computational searches, we report the prediction of a unique class of thermodynamically stable clathrate hydrides structures consisting of two previously unreported H 24 and H 30 hydrogen clathrate cages at megabar pressures. Among these phases, LaSc 2 H 24 shows potential hot superconductivity at the thermodynamically stable pressure range of 167 to 300 GPa, with calculated T c s up to 331 K at 250 GPa and 316 K at 167 GPa when the important effects of anharmonicity are included. The very high critical temperatures are attributed to an unusually large hydrogen-derived density of states at the Fermi level arising from the newly reported peculiar H 30 as well as H 24 cages in the structure. Our predicted introduction of Sc in the La-H system is expected to facilitate future design and realization of hot superconductors in ternary clathrate superhydrides.