High-temperature superconductivity in quinary clathrate hydrides under pressure

The search for high-temperature superconductivity among pressure-stabilized hydrides has received great interest since theory-directed clathrate hydrides, such as ${\mathrm{CaH}}_{6}, {\mathrm{YH}}_{6}, {\mathrm{YH}}_{9}$, and ${\mathrm{LaH}}_{10}$, were synthesized and shown to exhibit a superconducting critical temperature (${T}_{\mathrm{c}}$) above 200 K. However, further tuning the superconductivity and stability of these prominent hydrides to enhance their applicability remains a significant challenge. Here, taking the sodalitelike clathrate prototype $M{\mathrm{H}}_{6}$ ($M=\mathrm{Ca}$, Y, etc.) as an example, we investigate the stability and superconductivity of multicomponent metal hydrides containing four different metal atoms per structure. High-throughput simulations of 1820 $ABCD{\mathrm{H}}_{24}$ quinary hydrides, with initial symmetry of $F\overline{4}3m$ and varying metal atoms ($A, B, C$, and $D$), were conducted. The results identified 119 dynamically stable structures at 300 GPa, with 67 exhibiting superconductivity exceeding 200 K, and 20 having ${T}_{\mathrm{c}}$ values above 260 K. Notably, $(\mathrm{Na},\mathrm{Zr},\mathrm{Mg},\mathrm{Hf}){\mathrm{H}}_{6}$ is predicted to approach room temperature ${T}_{\mathrm{c}}$ at 250 GPa. Both configurational and vibrational entropy are crucial for stabilizing these alloys. $(\mathrm{Na},\mathrm{Y},\mathrm{Zr},\mathrm{Hf}){\mathrm{H}}_{6}, (\mathrm{Mg},\mathrm{Zr},\mathrm{Sc},\mathrm{Y}){\mathrm{H}}_{6}$, and $(\mathrm{Mg},\mathrm{Hf},\mathrm{Ca},\mathrm{Zr}){\mathrm{H}}_{6}$ were computed to be thermodynamically stable, making them promising candidates for experimental synthesis. These quinary superconducting hydrides may facilitate the realization of very high-temperature superconductors being stable over a broader range of conditions than binary or ternary systems.