Analysis of the internal and external contributions to the modes for both super-cells is very similar. Figure shows that percentage contribution from translational, rotational and vibrational (internal) motion to the first 300 modes of vibrations of DCI32a. It can be seen All polymorphs except Form III show strong absorption around 100 cm -1 , while Form III shows little absorption until above 130 cm -1 . Form II shows the strongest absorption of all the spectra.