CaNiN: Suppression of electronic instability by interchain coupling

CaNiN is a recently discovered compound that interestingly combines one-dimensional (1D) Ni-N chains in an unusual 3D arrangement. Although the linear chains could be a possible candidate for Peierls instability and, despite the formal ${\mathit{d}}^9$ configuration of Ni, this compound is found to remain metallic and paramagnetic down to very low temperatures. We present the results of electronic-structure calculations for CaNiN as obtained with the full-potential linearized-augmented-plane-wave method within the local-density approximation. Our results show that the interchain coupling strongly reduces the tendency towards electronic instabilities by introducing clear 2D and 3D features into the electronic structure of this compound. The states at the Fermi level are dominated by dpπ antibonding states. The dpσ antibonding bands, expected to be the highest band of the d-p complex, are depressed in energy by the interaction with conduction states (including states with interstitial character), and cannot be clearly singled out throughout the Brillouin zone.