Electronic structures and optical properties of hexagonal boron nitride under hydrostatic pressures

Electronic structures and optical properties of hexagonal boron nitride (h-BN) under hydrostatic pressure are studied using density functional theory calculations. Charge density difference, density of states, band structures, and dielectric functions are calculated to reveal the evolution of the electronic structures, band-gap, and optical properties of five typical stackings of h-BN corresponding to the hydrostatic pressures. The band-gap of h-BN decreases with the increasing hydrostatic pressure. The band-gap of h-BN with AA and AF stacking decreases faster than that of the others. The positions of their valence band maximum and the conduction band minimum shift in the Brillouin Zone corresponding to the external hydrostatic pressure, depending on the different stackings. In particular, the band structure of AA becomes direct at 9.19 GPa, which does not occur in other stackings. The band-edge optical absorption thresholds of AA, AD, AE, and AF show the redshift as the pressure increases, except for that of AB stacking, which is fluctuant. (C) 2011 American Institute of Physics. [doi:10.1063/1.3559300]