Librational Motion in Diatomic Molecular Crystals

Abstract

Analyses were made of the published experimental data of the heat capacity and other thermodynamic properties of crystals of simple diatomic molecules to obtain the frequency and the zero-point energy of the molecular libration in the crystalline state. It was found that the crystals of chlorine and heavier halogens have much larger librational force constant and much smaller zero-point energy relative to the static lattice energy than do the crystals of nitrogen, fluorine and carbon monoxide and that the differences in these characteristics are closely related to the differences in the crystal structure and polymorphism.