First principles study on the structural and optical properties of the high-pressure ZnO phases

A new high-pressure tetragonal phase ( B 10) of ZnO is investigated with an ab initio calculation based on density functional theory and is compared with the cubic B 1 (rocksalt structure) and B 2 (CsCl structure) phases at high pressure. It is found that the B 10 phase has a more covalent nature than the B 2 phase. The B 1, B 2, and B 10 phases are semiconductors and their band gap energies are determined to be 3.73, 3.15, and 3.27 eV, respectively. The B 10 phase has a similar optical response to the B 2 phase, but not the B 1 phase. The similarity of dielectric function between B 10 and B 2 phases are the result of the similar profiles of electronic density of state.