Disordered structure of the cubic phase of quinuclidine at 295 K

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Abstract
Single-crystal X-ray diffraction data were collected and interpreted for the plastic phase of quinuclidine at 295 K. The unit-cell is face-centred cubic with a = 8.913 Å, space group Fm3m. Assuming a rigid molecular skeleton, several types of orientational disorder were investigated : isotropic reorientations of the molecules about their centre of gravity and hindered reorientations between equally weighted orientations. For the second model, there is a fair agreement between observed and calculated structure amplitudes (residual R' =4.5 %); the packing has been found by a Monte Carlo method coupled with a rigid-group least-squares refinement. The threefold molecular and crystal axis do not coincide and there are 24 possible orientations for each molecule