The calculated C-C-S-H dihedral angles are reported in Table and can be compared with the experimental value for the ordered crystal observed at 30 K and for the disordered crystal measured at 293 K. 5 and terahertz spectra calculations reported later. For all subsequent calculations the unit-cell dimensions and the atomic positions were first fully optimised. One of these cells, DCI32a, was also used as the the starting point for the CP2K, molecular dynamics calculations, where it will be referred to as DCI32. Details of the spectra calculated for all the super-cells is available in section 7.8 of the SI.