Electronic structure of nitrogen-doped lutetium hydrides

Abstract

First-principles density functional theory (DFT) calculations of supercell structures based on N-doped Fm3¯mLuH3 reveal configurations of Fm3¯mLu8H23-xN that exhibit novel electronic properties such as flat bands, sharply peaked densities of states (van Hove singularities, vHs), and intersecting Dirac cones near the Fermi energy (EF). These electronic properties are present when N substitutes H in the octahedral interstices of Fm3¯mLuH3. These structures also exhibit an interconnected metallic hydrogen network, a common feature of high-Tc hydride superconductors. Electronic property systematics gives an estimate of Tc for one structure that is well above the critical temperatures predicted for structures considered previously. DFT+U has an especially strong effect on one of the structures considered, enhancing the vHs and flat bands near EF. These results provide a basis for understanding the electronic properties observed for nitrogen-doped lutetium hydride.