The recently synthesized compound ${\text{Na}}_3\text{N}$ has experimentally been shown to be semiconducting much in contrast to the outcome of standard density-functional theory calculations which find ${\text{Na}}_3\text{N}$ to be metallic. To address this obvious contradiction, we have systematically investigated the electronic structure of ${\text{Na}}_3\text{N}$ by density-functional calculations employing self-interaction-corrected pseudopotentials which have been shown before to yield results in much better agreement with experiment than standard local-density calculations. To assess the usefulness of such pseudopotentials for a broader class of related materials, we have carried out, in addition, a comparative ab initio study of the electronic structure of the nine alkali-metal fluorides MF, oxides ${\text{M}}_2\text{O}$, and nitrides ${\text{M}}_3\text{N}$ with $\text{M}=\text{Li}$, Na, and K. We arrive at valence and conduction bands that are in good agreement with the restricted results available in the literature from calculations going beyond the local-density approximation and from experiment. In particular, ${\text{Na}}_3\text{N}$ turns out to be clearly semiconducting, as observed in experiment.

• Received 25 June 2008

DOI:https://doi.org/10.1103/PhysRevB.78.125111