First-principles study of phase transition and band structure of ZrO2 under pressure

The sequent phase transition and band structure of ZrO2 under pressure are systematically investigated using first-principles simulations. The main findings are summarized as follows: (I) The monoclinic structure transforms to the tetragonal structure via a first-order phase transition and subsequently to the cubic structure via a second-order transition, which are driven by the dynamical instability. (II) Both monoclinic and tetragonal phases can display either indirect or direct band structures at different pressures, whereas the band gaps of cubic phase are always direct. Furthermore, as pressure increases, the band gap is enhanced for monoclinic and cubic phases and is reduced for tetragonal phase. Our calculated results are compared with the available theoretical data and good agreements are obtained.