Vibrational properties of cubic group-III nitrides: Force constants study

We study the lattice dynamics of the zinc-blende (ZB) allotropic form of bulk group-III nitrides using an approach based on the linear chain model. Supported by the fact that the longitudinal oscillations and the transverse oscillations are effectively decoupled, the relationship between the three dimensional (3D) and linear chain (1D) force constants has been reported. It is possible then to fit the 3D bulk force constants (and consequently the whole dynamical matrix) from the information related to few points, either experimental or theoretical. In particular, we derive the dispersion relation and the corresponding force constants of BN, AlN, GaN and InN. Our results are in good agreement with previous ab initio results.