The plastic phase of hexachloroethane, C2Cl6: a neutron powder and single-crystal investigation

Bragg intensity data extracted from energy-integrated neutron measurements were treated by a conventional split-atom model, with a series expansion in cubic harmonic functions, and by a Gaussian approximation for the molecular librations. The trigonal molecular axes are found to be smeared out close to cubic 111 axes with the Cl atoms near the 100 axes. With the three models mentioned consistent data are obtained for the root-mean-square translational amplitude: 0.4 Å, and the librational amplitude: 19.6°; both at 423 K. Data and results for three different temperatures are given.