Localization of Optical Phonons in Diamond Nanocrystals

We have developed a model for calculating the Raman spectra for optical phonons localized in diamond nanocrystals. The novelty of this approach is that it includes the contribution of localized phonons with dispersion over the entire Brillouin zone (3D model). The model is refined in that the phonon dispersion is calculated in the well-tested bond-charge model. The effects of the contribution to the Raman spectra from longitudinal optical phonons with frequencies higher than their frequency at the center of the Brillouin zone are considered. Comparative analysis of the calculated spectra and experimental spectra obtained from nanopowders and nanocrystalline diamond film is performed.