  The electronic structures and optical properties of cubic HfO2 are calculated
by means of generalized gradient approximation (GGA) +U approach. Without
on-site Coulomb interactions, the band gap of cubic HfO2 is 2.92eV, much lower
than the experimental value (5.7eV). Introducing the Coulomb interactions of 5d
orbitals on Hf atom (Ud) and of 2p orbitals on O atom (Up), we can reproduce
the experimental value of the band gap. The calculated dielectric function of
cubic HfO2 by the GGA+ Ud + Up approach predicts the presence of a shoulder
structure below the main peak of the absorption spectrum. These indicate that
the GGA +Ud +UP approach is a convenient and powerful method to calculate and
predict the electronic structures and the optical properties of wide-gap
optical materials.
