An investigation of the intermolecular modes in orthorhombic sulphur

An investigation has been made of the lattice dynamics of the molecular crystal orthorhombic sulphur. Coherent, inelastic neutron scattering experiments have been performed on a single-crystal specimen and the experimental results are reported and compared with computer model calculations of the dynamics. These calculations assume that the dynamics of sulphur can be formulated in terms of interactions between molecular groups of S8 rings which behave as rigid bodies. The interactions between non-bonded atom pairs are then described by a '6-exp' potential function. The model is also compared with available Raman data in terms of both frequency and intensity predictions. The agreement between calculation and experiment is particularly good for modes of the Gamma 1+ and Gamma 4+ representations.