Thermal and structural characterization of (CH3)(3)CCl

The polymorphism of(CH3)(3)CCl has been further investigated by both therma l and X-ray powder diffraction experiments. From the former, the phase tran sitions between the different phases (IV, III, II, I, and L) have been ther mally characterized, and in particular, the temperature domain of phase II has been settled to be from 217.9 to 219.8 K by means of C-p measurements. The structure of the lowest-temperature phase IV of (CH3)(3)CCl has been de termined by X-ray powder diffraction and Rietveld profile refinement. The s tructure, P2(1)/m with two molecules per unit cell, has been found to be is ostructural with that of phase II of (CH3)(3)CCN. The intermolecular intera ctions in the solid-state phases for (CH3)(3)CCl as well as for (CH3)(3)CCN have been analyzed by the study of the isobaric thermal-expansion tensor. The anisotropy of such interactions are discussed in the light of the previ ously studied dynamics disorder.