Raman Scattering and Dilatometric Studies of a Molecular Crystal Chloranil (C6Cl4O2)

The Raman scattering spectra and the thermal expansions of chloranil crystal were measured below and above the phase Transition point T 0 =93,8 K. The index of the transition parameter was obtained from the temperature dependence of the soft mode frequency for 0.08<( T 0 - T )/ T 0 <0.89 as β=0.47±0.05, including within its range the mean-field value 0.5.