Infrared reflectance spectrum of BN calculated from first principles

Using the linear response theory, vibrational and dielectric properties are calculated for c-BN, w-BN and h-BN. Calculations of the zone-center optical-mode frequencies (including LO-TO splittings) are reported. All optic modes are identified and excellent agreement is found between the theory and experimental results. The static dielectric tensor is decomposed into contributions arising from individual infrared-active phonon modes. It is found that all the structures have a smaller lattice dielectric constants than those of the electronic contributions. Finally, the infrared reflectance spectrums are presented. Our theoretical results indicate that w-BN shows a similar reflectivity spectrum as c-BN. It is difficult to tell apart the wurtzite structure from the zinc blende phase by IR spectroscopy.