First-Principles Design of Halide-Reduced Electrides: Magnetism and Topological Phases

We propose a design scheme for seeking potential electrides derived from conventional materials. Starting with rare-earth element based halides, we exclude the halogen and perform global structure optimization to obtain stable phases but having an excess of electrons confined inside interstitial cavities. Then, spin-polarized interstitial states are realized by chemical substitution with magnetic lanthanides. Interestingly, the band-topology analysis for the predicted systems evidences the possible emergence of topological magnetism in these electrides. We report two families of designed electrides, $A_2$C$_2$ and $A_2$Ge ($A=$ Y or Gd), both of which turn out to be topological nodal line semimetals (metals) in the absence of spin-orbit coupling and manifest spin-polarized interstitial states with the inclusion of Gd. Our work establishes an alternative computational approach of functional electrides design and highlights the magnetism and topological phases embedded in electrides.