Properties of strained and unstrained III-nitrides

We present results of first-principles calculations of structural, dielectric and lattice-dynamical properties of the group-III nitrides BN, AlN and GaN. We consider both polytypes, the zinc-blende and the wurtzite structure, under hydrostatic pressure. The calculations within density-functional theory and local-density approximation are based on soft pseudopotentials and plane waves. We determine the Born effective charges, the high-frequency dielectric constants and the zone-center phonons.