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, an d BN is studied using the adiabatic bond-charge model. The resulting phonon spectra for zinc-blende GaN and AIN compare very well with ab initio calcu lations along symmetry directions. We discuss the effect of the internal pa rameter u on the A(1)(LO) and E-1(LO) modes. We also present the angle depe ndence of the zone-center optical-phonon modes in the wurtzite phase. The a nticrossing behavior of the A(1) acoustic and E-2 optical modes is also dis cussed.