Molecular dynamics calculations for solid bicyclo (2.2.2) octane

The properties of bicyclo (2.2.2) octane (BCO) are investigated using constant pressure molecular dynamics calculations and various intermolecular potentials based upon atom-atom or site-site interactions. Starting from an assumed low temperature trigonal structure, isobaric heating at low pressures yields a structural phase transition to a cubic rotator phase at about 170 K, in excellent agreement with experiment. The reorientational dynamics of individual BCO molecules have been investigated in the resulting cubic rotator phase. The relaxtation time τ4, for reorientation of the molecular C 3 axis from one [111] direction to another has been studied along with the reorientation time, τ3, associated with molecular rotation about the C 3 axis. Both relaxation times, which are model dependent, are longer than a picosecond, in fair agreement with experiment. Finally, the power spectra associated with translational and rotational motions have been computed. The merits of the various intermolecular force models are discussed.