Vibrational spectra of the α-crystalline phase of hexafluoroethane

A synthesis of spectral evidence and x‐ray data has resulted in the solution of the crystal structure of the a form of hexafluoroethane. The space group is $C_{\text{2h}}^2$ with two molecules in the unit cell located on C_i sites. The unit‐cell dimensions are a = 9.3 Å, b = 5.1 Å, and c = 4.6 Å. There is disorder in the a crystal which was determined to be of the statistical variety. The spectra of the a form verified the symmetry aspects of the theory governing solid‐state vibrational spectroscopy, but the approximate dipole‐dipole theory was shown to partially fail in explaining even the relative magnitudes of the splittings in the nondegenerate modes. This failure was ascribed to atom‐atom interactions in the crystal.