One‐Dimensional Hydrogen Chains in Li–Hf–H System: A Pathway to High Superconductivity Under High Pressure

Abstract The recent discovery of high‐critical‐temperature (high‐ T _c ) superconductivity in hydrides such as H ₃ S and LaH ₁₀ has significantly advanced the quest for room‐temperature superconductors. This work reports a new class of high‐ T _c hydrides in the Li–Hf–H system characterized by unknown one‐dimensional (1D) hydrogen chains. Through structure prediction methods and first‐principles calculations, the thermodynamically stable compound LiHfH ₂₀ is discovered, exhibiting a remarkable T _c of 222 K at 260 GPa. Notably, the distinct 1D hydrogen chains in LiHfH ₂₀ facilitate strong coupling between high‐frequency phonon modes and hydrogen‐derived electronic states near the Fermi level, significantly enhancing superconductivity. Extending this concept to other MX H ₂₀ compounds ( M and X represent the other 27 elements), it is demonstrated that hole doping further increases the T _c , exemplified by isostructural BeCaH ₂₀ , which achieves a T _c of 262 K. These findings provide novel and viable high‐pressure hydrides with 1D hydrogen chain for future experimental synthesis toward room‐temperature superconductivity.