Advanced Chemistry

Two-dimensional (2D) electrides, emerging as a new type of layered material whose electrons are confined in interlayer spaces instead of at atomic proximities, are receiving interest for their high performance in various (opto) electronics and catalytic applications. A realization of electrides containing anionic electrons has been a great challenge because of their thermodynamic stability. For example, experimentally, only a couple of layered nitrides and carbides have been identified as 2D electrides. We developed a material by design scheme and applied it to the computational exploration of new low-dimensional electrides. Our approach here offers an important alternative that overcomes the current limitation on discovery of new 2D inorganic electrides. By combining the global structure optimization method and first-principles calculations, we identified new thermodynamically stable electrides that are experimentally accessible. Most remarkably, we, for the first time, reveal an effective design rule for 2D electrides. We then discover another new class of electrides, the first electride with nontrivial band topology, based on 1D building block by coupling materials database searches and first-principles-calculations-based analysis. This new class of electrides, composed of 1D nanorod building blocks, has crystal structures that mimic β-TiCl₃ with the position of anions and cations exchanged. Unlike the weakly coupled nanorods of β-TiCl₃, Cs₃O and Ba₃N retain 1D anionic electron along the hollow inter-rod sites; additionally, strong inter-rod interaction in C₃O and Ba₃N induces band inversion in a 2D superatomic triangular lattice, resulting in Dirac nodal lines. Our work represents an important scientific advancement over previous knowledge of realizing electrides in terms of both materials and design principles, and should interest the communities of catalytic chemistry, surface physics, and structural chemistry, as well as the related engineering disciplines.