Because of the relatively short simulation times and the size of the simulation cell, it is common practice to apply a window filter to the dipole moment correlation function. This window ensures that the dipole moment decays as it would in a real system, with the decay constant linked to the lifetime of the phonons and the width of peaks. The fact that this is imposed on the system means that peak widths are not a true reflection of the phonon lifetimes. Having said that the comparison of the 88 K and 300 K MD simulations of Form I did show some vibrational broadening that is not just a function of the windowing function and provides calculated spectra with widths comparable to those observed experimentally.