Crystal structure and lattice dynamics of chlorine The role of electrostatic and anisotropic atom-atom potentials

Abstract

An extensive analysis of the intermolecular forces in the chlorine crystal has been performed. Different models of the intermolecular potential, including anisotropic terms and electrostatic contributions from multipoles higher than quadrupole have been taken into account and tested for their ability to reproduce static and dynamical properties of solid chlorine. The inclusion of anisotropic dispersion forces reproduces correctly the orthorhombic unit cell. Anisotropic terms are required also in the short range repulsive atom-atom interactions to obtain a good fit to lattice frequencies and stability of the Cmca structure with respect to a hypothetical cubic phase. A tensor formalism, particularly convenient for dynamical calculations, is developed and used to describe angular dependent atom-atom interactions.