Theoretical Insights into High-<i>T</i>_c Superconductivity of Structurally Ordered YThH₁₈: A First-Principles Study

There has been a marked increase in interest in high-temperature superconductors over the past few years, sparked by their potential to revolutionize multiple fields, including energy generation and transportation. A particularly promising avenue of exploration has emerged in the form of ternary superhydrides, compounds composed of hydrogen along with two other rare-earth elements. Our investigation focuses on the search for Y-Th-H ternary compounds; employing an evolutionary search methodology complemented by electron-phonon calculations reveals a stable superhydride, <i>P</i>6̅<i>m</i>2-YThH₁₈, capable of exhibiting a critical temperature (<i>T</i> _c) as high as 222 K at 200 GPa along a few low-<i>T</i> _c novel hydrides. Our analysis explores the possibility of alloyed structure formation from the disordered condition of Th-doped YH₉ and establishes that the <i>P</i>6̅<i>m</i>2-YThH₁₈ is indeed a structurally ordered structure. This opens up an exciting avenue for research on multinary superhydrides, which could facilitate experimental synthesis and provides potential implications for high-temperature superconductivity research.