The SH...O hydrogen bonding motif shows a shift to lower frequency relative to the SH...S bonding motif around 3000 cm -1 and to higher frequency for the absorption at about 3200 cm -1 associated with an NH...O hydrogen bond. For the SH...S bonding pattern there is a doublet pattern of absorption associated with the S-H bond between 2430 cm -1 to 2460 cm -1 . Whilst for the SH...O pattern there is a single, weaker peak at 2560 cm -1 for the SH...O hydrogen bonded pattern. The SI compares the calculated spectra of the two hydrogen-bonding motifs over the full frequency range. shows the lowest frequency absorption while Form II shows the highest, a direct comparison is made particularly difficult here because of the very large spectral linewidths that are observed in the dynamic calculations, however, unlike in the terahertz spectral region, the overall integrated intensities and spectral shape are similar in both plots. Finally, Figure (e) shows the dynamic calculated spectra for the disordered super-cell of Form I, DCI32a. The inclusion of disorder increases the spectral widths compared to the dynamic calculation without disorder but both show three peaks centred at approximately 2500 cm -1 , 3000 cm -1 and 3250 cm -1 . One thing of special interest in this spectral region is that, although its difficult to make a direct comparison in intensities between the static and dynamic calculations because of the differing widths, the integrated spectral intensities are similar in both types of calculations unlike the terahertz spectral region where large differences were observed.