First-principles study on structural, dielectric, and dynamical propertiesfor three BN polytypes - art. no. 115207

We report the results of first-principles calculations on the structural pr operties (lattice constants and internal parameters), dielectric properties (macroscopic and static dielectric constants, and Born effective charge te nsors), and dynamical properties (Gamma -phonon frequencies) for the three polytypes of BN: the cubic zinc-blende structure (c-BN), the wurtzite struc ture (w-BN), and the hexagonal structure (h-BN). Our calculations were perf ormed with the ultrasoft pseudopotential method and the linear response app roach based on density-functional perturbation theory. By comparing the coh esive energies, we found that the c-BN structure is the most stable among t he three polytypes at zero temperature. The computed equilibrium structural parameters, bulk moduli, and dielectric properties are in good agreement w ith the experimental data except for the lattice constant c of h-BN and the macroscopic dielectric constant along the c axis of h-BN. The Gamma -phono n frequencies of c-BN and,v-BN are close to each other. In order to disting uish c-BN and w-BN by Raman spectroscopy, it turns out that we should inves tigate the two Raman active E-2 modes that exist only in w-BN.