Electronic structure of calcium hexaboride within the weighted density approximation

We report calculations of the electronic structure of ${\mathrm{CaB}}_6$ using the weighted density approximation (WDA) to density-functional theory. We find a semiconducting band structure with a sizable gap, in contrast to local-density approximation (LDA) results, but in accord with recent experimental data. In particular, we find an X-point band gap of 0.8 eV. The WDA correction of the LDA error in describing the electronic structure of ${\mathrm{CaB}}_6$ is discussed in terms of the orbital character of the bands and the better cancellation of self-interactions within the WDA.