Phonons in zinc-blende and wurtzite phases of GaN, AlN, and BN with the adiabatic bond-charge model

The lattice dynamics of the zinc-blende and wurtzite phases of GaN, AlN, and BN is studied using the adiabatic bond-charge model. The resulting phonon spectra for zinc-blende GaN and AlN compare very well with ab initio calculations along symmetry directions. We discuss the effect of the internal parameter u on the A₁(LO) and E₁(LO) modes. We also present the angle dependence of the zone-center optical-phonon modes in the wurtzite phase. The anticrossing behavior of the A₁ acoustic and E₂ optical modes is also discussed.