Correlation Effects on Coupled Electronic and Structural Properties of Doped Rare-Earth Trihydrides

Rare-earth trihydrides exhibit intriguing coupled electronic and structural properties as a function of doping, hydrogen vacancies, and thermodynamic conditions. Theoretical studies of these materials typically rely on density functional theory (DFT), including the use of small supercells that may underestimate strong correlation effects and structural distortions which in turn may influence their metallicity. Previous work has shown hybridization-induced flat bands near the Fermi energy by particular anion arrangements. Here, we elucidate the roles of lattice distortions and correlation effects on the electronic properties of pristine and doped $R$H$_3$ by adopting DFT+U and Quantum Monte Carlo (QMC) methods. Large Hubbard parameters for hydrogen and nitrogen orbitals are computed, indicating strong correlation effects.