Hydrogen Clathrate Structures in Rare Earth Hydrides at High Pressures: Possible Route to Room-Temperature Superconductivity

TLDR

Room‑temperature superconductivity remains a key goal, with recent 200 K superconductivity in compressed hydrogen sulfides showing that H‑rich materials under high pressure can achieve such temperatures. The study aims to identify stable hydrogen‑rich clathrate structures in rare‑earth hydrides at high pressures via first‑principles searches. These clathrates feature unusual H cages (H24, H29, H32) with weak covalent H–H bonds, where rare‑earth atoms sit at cage centers. The YH10 clathrate (YH32) is predicted to be a room‑temperature superconductor with Tc up to 303 K at 400 GPa, driven by high H‑derived DOS and strong electron‑phonon coupling from H cage motions.

Abstract

Room-temperature superconductivity has been a long-held dream and an area of intensive research. Recent experimental findings of superconductivity at 200 K in highly compressed hydrogen (H) sulfides have demonstrated the potential for achieving room-temperature superconductivity in compressed H-rich materials. We report first-principles structure searches for stable H-rich clathrate structures in rare earth hydrides at high pressures. The peculiarity of these structures lies in the emergence of unusual H cages with stoichiometries H_{24}, H_{29}, and H_{32}, in which H atoms are weakly covalently bonded to one another, with rare earth atoms occupying the centers of the cages. We have found that high-temperature superconductivity is closely associated with H clathrate structures, with large H-derived electronic densities of states at the Fermi level and strong electron-phonon coupling related to the stretching and rocking motions of H atoms within the cages. Strikingly, a yttrium (Y) H_{32} clathrate structure of stoichiometry YH_{10} is predicted to be a potential room-temperature superconductor with an estimated T_{c} of up to 303 K at 400 GPa, as derived by direct solution of the Eliashberg equation.