The band structures and optical properties of monoclinic HfO2 areinvestigated by the local density approximation (LDA)+U approach. With theon-site Coulomb interaction being introduced to 5d orbitals of Hf atom and 2porbitals of O atom, the experimental band gap is reproduced. The imaginary partof the complex dielectric function shows a small shoulder at the edge of theband gap, coinciding with the experiments. This intrinsic property ofcrystallized monoclinic HfO2, which is absent in both the tetragonal phase andcubic phase, can be understood as a consequence of the reconstruction of theelectronic states near the band edge following the adjustment of the crystalstructure. The existence of a similar shoulder-like-structure in the monoclinicphase of ZrO2 is predicted.
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