2.3 Molecular dynamics simulations Simulation models for the two FSPA solvates were built using the atomic coordinates and unit cell parameters obtained by XRD at 120 K (corresponding CIF files are supplied in the data archive). An ethanol or acetone solvent molecule was manually placed in the void in the FSPA unit cell (i.e., modelling 100% solvent occupancy), and simulation boxes were made up of 9 x 3 x 3 unit cells and contained 162 FS, 162 PA and 81 solvent molecules. To assess the importance of the sulfonamide disorder depicted in Fig. , pairs of simulations were created for both systems, containing uniquely one orientation or the other, with the NH2 of the sulfonamide either facing pointing towards the solvent channel (model A) or away from it (model B). Although the physical system will contain a random distribution of sulfonamide orientations, these artificial fully ordered systems can be expected to span the range of possible solvent dynamics.