Electronic characteristics of quasi-2D metallochloronitrides: NaxHfNCl (Tc=25 K)

Local density functional results are presented for the electron-doped metallochloronitrides AxZrNCl and AxHfNCl, A=Li or Na, which superconduct up to 25 K. The alkali non-stoichiometry is treated in a virtual crystal approximation. The electronic structure is strongly two dimensional, especially in the conduction band region occupied by the carriers, because the states are formed from the in-plane orbitals dxy, dx2−y2 of the metal ion and the px, py orbitals of the N ion. We predict a change of behavior at a doping level of x=0.3.