The correlated band theory implemented as a combination of the local density approximation with the exact diagonalization of the Anderson impurity model is applied to PuO${}_2$. We obtain an insulating electronic structure consistent with the experimental photoemission spectra. The calculations yield a band gap of 1.8 eV and a nonmagnetic singlet ground state that is characterized by a noninteger filling of the plutonium $f$ shell ($n_f\approx 4.5$). Due to sizable hybridization of the $f$ shell with the $p$ states of oxygen, the ground state is more complex than the four-electron Russell-Saunders ${}^5{I}_4$ manifold split by the crystal field. The inclusion of hybridization improves the agreement between the theory and experiment for the magnetic susceptibility.

• Received 30 September 2013

DOI:https://doi.org/10.1103/PhysRevB.89.041109