Infrared reflectance spectrum of BN calculated from first principles

Using the linear response theory, vibrational and dielectric properties are calculated for cc-BN, ww-BN and hh-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 ww-BN shows a similar reflectivity spectrum as cc-BN. It is difficult to tell apart the wurtzite structure from the zinc blende phase by IR spectroscopy.