Lattice dynamics of sulphur dioxide using a rigid molecule model

Abstract

Lattice dynamics calculations on the orthorhombic crystal SO2 are presented. The model assumes rigid molecules with Lennard-Jones interactions between atoms and also electrostatic interactions between point dipoles placed on atomic centres. The oxygen atom dipoles point along the O—S bonds, and resultant molecular dipole and quadrupole moments are consistent with experimental values. The parameters of the model are optimized to give a least-squares fit to observed zone centre frequencies, equilibrium conditions, and lattice energy. It is found that small variations of the experimental lattice parameters allow significant improvement in modelling the stability of the lattice. Dispersion curves obtained for this model are shown for the principal symmetry directions.