LATTICE-DYNAMICS OF CYANOGEN

A simple force constant model is described and applied to the vibrations of crystalline cyanogen, C2N2, at low temperatures. The model uses eleven adjustable parameters (six intermolecular and five intramolecular) to calculate the frequencies of seventeen lattice modes and twenty-eight components of internal modes, and reasonable agreement with spectroscopic data is obtained. Although cyanogen shows many of the characteristics of a typical molecular crystal, there is some evidence that its large quadrupole moment results in longer-range forces being more significant than usual, particularly in contributing to the splittings of some internal modes.