Potential energy calculations of the rotational barriers of molecular solids. II. The dynamic structures of adamantane and hexamethylenetetramine in the solid state and the nature of the phase transition in adamantane

Abstract

Nonbonded atom–atom potential functions have been used in conjunction with literature crystal structure data from diffraction measurements to calculate the sublimation energies and also the energy barriers for rotation around the molecular axes for both α and β phases of adamantane and also for hexamethylenetetramine. These results are compared with experimental values and the nature of the dynamic structures deduced.In addition, a detailed consideration of individual intermolecular interactions in the case of adamantane is presented which explains in detail the observed high temperature disordered structure and the nature of the associated order–disorder transition.