High-temperature superconductivity of Pm3¯n Lu4H23 immersed in an as-synthesized lutetium polyhydride

The precompression effect of foreign elements affords a promising route to metallizing hydrogen atoms under moderate pressure and achieving superconductivity with high transition temperature $({T}_{\mathrm{C}})$ in polyhydrides. Recently, lutetium (Lu) polyhydrides are receiving considerable attention due to their fully filled $f$ orbitals, which are favorable for realizing high ${T}_{\mathrm{C}}$. The highest ${T}_{\mathrm{C}}$ observed in the as-synthesized lutetium polyhydrides up to now has reached 65--71 K under pressures of 181--218 GPa, which was attributed to the $Pm\overline{3}n$ ${\mathrm{Lu}}_{4}{\mathrm{H}}_{23}$ phase but without computational analysis. Here we perform first-principles calculations on the bonding feature, the stability, the electronic property, and the superconductivity of ${\mathrm{Lu}}_{4}{\mathrm{H}}_{23}$. ${\mathrm{Lu}}_{4}{\mathrm{H}}_{23}$ presents robust metallicity due to the orbital hybridizations associated with the H-H covalent and Lu-H ionic bonds, as well as the charge transfer from Lu to H atoms. Our calculations reveal that ${\mathrm{Lu}}_{4}{\mathrm{H}}_{23}$ can be stabilized at pressures above \ensuremath{\sim}200 GPa, whose ${T}_{\mathrm{C}}$ is estimated to be 69--225 (103--210) K at 200 (218) GPa and maintains at the average values around 150--200 K under the pressures exceeding 250 GPa. We propose that the $Fm\overline{3}m$ LuH plays a possible role in stabilizing ${\mathrm{Lu}}_{4}{\mathrm{H}}_{23}$ at pressures lower than 200 GPa, and, simultaneously, decreases the ${T}_{\mathrm{C}}$ of superconductivity in the as-synthesized lutetium polyhydrides. Our work provides a computational analysis on ${\mathrm{Lu}}_{4}{\mathrm{H}}_{23}$, and the predicted high ${T}_{\mathrm{C}}$ is expected to be experimentally realized by increasing pressure and optimizing synthesis process to eliminate the LuH phase.