Lattice Dynamics of Nitrogen and Carbon Dioxide

A simple force constant model is used to calculate the normal mode frequencies and eigenvectors of the cubic crystals α‐N₂ and CO₂. Good agreement with spectroscopic data is obtained for the lattice frequencies, and crystal field splittings of the molecular modes are found to be small in all cases. For α‐N₂, the calculations suggest that the non‐centrosymmetric structure is more likely, but the possibility that this result is merely a consequence of the larger number of parameters involved cannot be ruled out. For CO₂, the intermolecular CO interactions appear to play a relatively minor role.