Tetragonal high-pressure phase of ZnO predicted from first principles

We report a high-pressure tetragonal PbO-type structure (B10) of ZnO predicted through ab initio lattice-dynamics calculation. This structure can be directly transformed from NaCl structure (B1) along an orthorhombic Pmmn transition path and can be viewed as alternatively stacked layers of cations and anions with the anion layer composed of zigzag arranged anionic rows. Enthalpy curve calculation suggests that B10 is stable in a large pressure range of 236-316 GPa, above which CsCl structure (B2) takes over. Band-structure calculation reveals that this polymorph is a wide band-gap semiconductor with an energy gap larger than 2.95 eV.