Potential high- <i> T _c </i> superconducting lanthanum and yttrium hydrides at high pressure

A systematic structure search in the La-H and Y-H systems under pressure reveals some hydrogen-rich structures with intriguing electronic properties. For example, LaH₁₀ is found to adopt a sodalite-like face-centered cubic (fcc) structure, stable above 200 GPa, and LaH₈ a <i>C</i>2/<i>m</i> space group structure. Phonon calculations indicate both are dynamically stable; electron phonon calculations coupled to Bardeen-Cooper-Schrieffer (BCS) arguments indicate they might be high-<i>T</i>_<i>c</i> superconductors. In particular, the superconducting transition temperature <i>T</i>_<i>c</i> calculated for LaH₁₀ is 274-286 K at 210 GPa. Similar calculations for the Y-H system predict stability of the sodalite-like fcc YH₁₀ and a <i>T</i>_<i>c</i> above room temperature, reaching 305-326 K at 250 GPa. The study suggests that dense hydrides consisting of these and related hydrogen polyhedral networks may represent new classes of potential very high-temperature superconductors.