Superconducting properties of Li₂KH₁₇ with a cage configuration under high pressure

The search for room-temperature superconductors in high-pressure hydrides is of significant scientific importance. Here, we systematically studied the Li-K-H system using a genetic algorithm combined with density functional theory calculations. At 150 GPa, the stable phases identified are <i>Pmma</i>-Li₂K₂H₄, <i>P</i>6̄2<i>m</i>-LiK₃H₃, <i>P</i>6̄-LiK₃H₄, <i>P</i>1-LiK₃H₆ and <i>R</i>3<i>m</i>-Li₃K₂H, while at 300 GPa, the stable phases are <i>C</i>2/<i>m</i>-LiK₃H₈, <i>Fd</i>3̄<i>m</i>-Li₂KH₁₇, <i>R</i>3<i>m</i>-Li₂K₂H and <i>Cm</i>-Li₃KH. Our results revealed that <i>Fd</i>3̄<i>m</i>-Li₂KH₁₇, featuring H₂₀ and H₂₈ cages, exhibits excellent superconducting properties due to strong electron-phonon coupling, achieving a critical temperature (<i>T</i>_c) of 238 K at 200 GPa. Furthermore, <i>ab initio</i> molecular dynamics simulations indicate that <i>Fd</i>3̄<i>m</i>-Li₂KH₁₇ enters a superionic state at 800 K and 200 GPa. And hydrogen atoms vibrate at ring vertices and hop between them, creating continuous femtosecond-scale trajectories within the cage framework. These findings deepen our understanding of the various properties exhibited by hydrides under high pressure and provide valuable clues for studying the properties of high-pressure hydrides.