Possible High-Temperature Superconductivity inLi2CuH6 at Ambient Pressure

Wetheoretically investigate the structural stability, electronic property, and superconductivity of the hydrogen-rich compound Li2CuH6 in its face-centered cubic phase. First-principles calculations show that Li2CuH6 is thermodynamically metastable atambient pressure but dynamically stable. Moreover, ab initio molecular dynamics (AIMD) simulation at 300 K further confirms that Li2CuH6 remains structurally intact without decomposition. These findings demonstrate that it may be synthesized underhigh pressure and retained upon decompression. The material is identified as thermodynamically metastable but dynamicallystable at ambient pressure, indicating that it may be synthesized under compression and retained after release. Moreover, Li2CuH6 exhibits metallic behavior with a flat band and a van Hove singularity (vHS) near the Fermi level, and Fermi-surface states dominated by Cu–d and H–s orbitals, promoting strong electron–phonon interactions. Phonon calculations reveal that hydrogenvibrations provide the primary contribution to the coupling, yielding a large electron–phonon coupling constant. Insights into thesuperconducting temperature (Tc) are obtained using various theoretical approaches, which estimate Tc to be in the range of104–152 K. Bonding analysis further indicates mixed covalent–ionic character within Cu–H octahedra. These results highlightLi2CuH6 as a promising hydrogen-based metastable superconductor for future experimental exploration.