The electronic structure and properties of protactinium and its oxides (PaO and PaO2) have
been studied within the framework of the local density approximation (LDA), the
Perdew–Burke–Ernzerhof generalized gradient approximation [GGA(PBE)], LDA C U and
GGA(PBE) C U implementations of density functional theory. The dependence of selected
observables of these materials on the effective U parameter has been investigated in detail.
The examined properties include lattice constants, bulk moduli, the effect of charge density
distributions, the hybridization of the 5f orbital and the energy of formation for PaO and PaO2.
The LDA gives better agreement with experiment for the bulk modulus than the GGA for Pa
but the GGA gives better structural properties. We found that PaO is metallic and PaO2 is a
Mott–Hubbard insulator. This is consistent with observations for the other actinide oxides. We
discover that GGA and LDA incorrectly give metallic behavior for PaO2. The GGA(PBE) + U
calculated indirect band gap of 3.48 eV reported for PaO2 is a prediction and should stimulate
further studies of this material.