Raman spectra of BN nanotubes: Ab initio and bond-polarizability model calculations

We present ab initio calculations of the nonresonant Raman spectra of zigzag and armchair BN nanotubes. In comparison, we implement a generalized bond-polarizability model where the parameters are extracted from first-principles calculations of the polarizability tensor of a BN sheet. For light polarization along the tube axis, the agreement between model and ab initio spectra is almost perfect. For perpendicular polarization, depolarization effects have to be included in the model in order to reproduce the ab initio Raman intensities