Cyanogen: structure, dynamics and inter-molecular potentials

Abstract

The crystal structure of cyanogen at 15 K has been determined using neutron power profile measurements. This new structural information and the recently determined quadrupole moment have been included in revised calculations of the lattice dynamics. A satisfactory description of both the crystal structure and the dynamics cannot be obtained with any of the models used for the inter-molecular forces. The model giving the 'best' fit has potential parameters very different from those in the literature. The present results indicate that the concept of transferable potentials is not valid, at least in its simple form. Lattice frequencies, electrostatic interactions and low-temperature crystal structure data must all be included in the database if transferable nonbonded, atom-atom potential are to be a valid and useful concept.