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.