Lattice dynamics and spectral line widths of α-N2

Abstract

The lattice dynamics of α-N₂ has been studied, using a potential of the atom-atom form which had previously been calibrated to fit the known properties of the solid. Special features encountered in the treatment of librational motions are discussed. Interactions between translational and librational motions are of great importance in determining the dispersion curves and densities of states. A study of two-phonon densities together with the experimental observations of line widths in the optical spectra of the solid leads to the conclusion that there is a considerable difference in the anharmonicities of the two infra-red active translational modes. It is also concluded that the librational modes are much more anharmonic than the translational modes.