First principles calculations of the electronic structure of ZrN allotropes

The atomic structures and electronic properties of different ZrN allotropes, including face-centered cubic ZrN (B1 ZrN), hypothetic wurtzite (w) ZrN, and hypothetic two-dimensional (2D) and three-dimensional (3D) layered hexagonal (h) ZrN, are investigated by systematic first-principles calculations. Although the cohesive energy calculation indicates that the B1 ZrN is more stable than the hypothetic w-ZrN and h-ZrN, we suggest that the monolayer h-ZrN may be stable on some substrates. Charge population analysis shows that the polar, covalent bonding character appears between N atoms and Zr atoms for all ZrN allotropes involved in this paper. A Van Hove singularity (VHS) with a high density of states (DOS) locating at 0.2 eV above the Fermi level appears for monolayer h-ZrN, which results from a saddle point of the partially occupied Zr-dz² energy bands due to lack of interlayer interaction. Such a VHS observed in the monolayer h-ZrN indicates that this hypothetic monolayer material might be a potential candidate for new superconducting material by electron doping.