Theoretical Insights into High‑<i>T</i><sub>c</sub> Superconductivity of Structurally Ordered YThH<sub>18</sub>: A First-Principles Study

There has been a marked increase in interest in high-temperature\nsuperconductors over the past few years, sparked by their potential\nto revolutionize multiple fields, including energy generation and\ntransportation. A particularly promising avenue of exploration has\nemerged in the form of ternary superhydrides, compounds composed of\nhydrogen along with two other rare-earth elements. Our investigation\nfocuses on the search for Y–Th–H ternary compounds;\nemploying an evolutionary search methodology complemented by electron–phonon\ncalculations reveals a stable superhydride, <i>P</i>6̅<i>m</i>2-YThH<sub>18</sub>, capable of exhibiting a critical temperature\n(<i>T</i><sub>c</sub>) as high as 222 K at 200 GPa along\na few low-<i>T</i><sub>c</sub> novel hydrides. Our analysis\nexplores the possibility of alloyed structure formation from the disordered\ncondition of Th-doped YH<sub>9</sub> and establishes that the <i>P</i>6̅<i>m</i>2-YThH<sub>18</sub> is indeed\na structurally ordered structure. This opens up an exciting avenue\nfor research on multinary superhydrides, which could facilitate experimental\nsynthesis and provides potential implications for high-temperature\nsuperconductivity research.