Ab initio investigations on the electronic structure and optical properties of HX-ZnO

First-principles ultrasoft pseudopotential method is applied to study HX ZnO, which has a novel graphite like hexagonal structure transformed from wurtzite (WZ) phase under tensile stress along direction or compressive stress along 0001] direction. The electronic structure and optical properties, including dielectric function, reflectivity and absorption coefficient, of HX ZnO are calculated and compared with those of WZ ZnO under the given uniaxial stress. It is found that HX ZnO is an indirect semiconductor, being different from WZ ZnO. HX ZnO has a dielectric response different from WZ ZnO at ambient conditions or under the given uniaxial stress, especially in the case of E∥c. Similar variation is also observed in the reflectivity and absorption coefficient. The variation in the optical properties is attributed to the additional ZnO bond along c-axis HX ZnO.