A DFT-LDA study of electronic and optical properties of hexagonal boron nitride under uniaxial strain

Using local density approximation (LDA) within the framework of density functional theory, we investigate the response of the electronic and optical properties of hexagonal boron nitride to external uniaxial strain along c-axis. Five typical stable stackings are considered. The band gap of all the five stackings decreases as the uniaxial pressure increases, and the band gap of AA, AE and AF reduce faster than that of the others. We find that the response of band dispersion of AB to the uniaxial compression is different from that of the others. The band-edge absorption threshold of AB red shifts initially and starts to blue shift at 10.53 GPa, whereas the threshold of the other stackings only shows red shift under the uniaxial pressure. The band structure of AA changes from indirect to direct when the uniaxial pressure is larger than 6.55 GPa. Moreover, the band structure of AE changes from quasi-direct to indirect under the uniaxial compression.