Phonon spectrum of boron nitride with wurtzite structure

Using the quantum mechanics methods the interatomic force constants for the rigid-ion model of boron nitride with wurtzite structure are calculated. An analysis of the symmetry of the fundamental vibrations of the lattice is performed by construction of the projection operators. The calculations of the phonon dispersion relations along seven directions of high symmetry of this lattice are carried out in the harmonic approximation. In terms of this model the phonon state density and the specific heat temperature dependence are determined for boron nitride with wurtzite structure, the results being in good agreement with the experimental data on the specific heat. (author)