Raman effects under pressure in chloroadamantane plastic crystal

Raman scattering experiments have been performed on orientationally disordered crystal chloroadamantane under pressure. Investigations carried out in both the lattice-mode and the internal-mode regions have shown that this plastic crystal exhibits spectroscopic features common to most molecular solids. The pressure-induced disorder-order phase transition around 0.5 GPa has been analysed using crystallographic and Raman data in the low-temperature phase. Additional features were observed with further compression above 8 GPa. Two different hypotheses are proposed to explain these features. (author)