First-principles study of high-pressure phonon dispersions of wurtzite, zinc-blende, and rocksalt AlN

We present ab initio calculations of the phonon dispersions and density of states for wurtzite, zinc-blende, and rocksalt AlN under hydrostatic pressure using density functional perturbation theory. The calculations predict the full phonon dispersions throughout the Brillouin zone. Out results regarding zone-center modes for wurtzite and zinc-blende structures show generally good agreement with Raman measurements and previous theoretical data. For rocksalt structure, the present results are predictions. The different behavior of the lattice vibration properties under pressure in the three phases being studied here is discussed. The pressure coefficients and mode Gruneisen parameters are determined from the pressure dependence of vibration modes. (c) 2008 American Institute of Physics.