As our crystal structures solved from the coarse-grained model were at unrealistic densities (≈ 0.6 g cm -3 ) we used the molecule to crystal function in CrystalMaker® with the DFT optimised molecule, to create the two crystal structures. The crystal structures were created such that the density was maximised without any overlap between the cage molecules within the crystal structure, leading to crystal structures with the lattice parameters a = 20.5 Å, c = 14.1 Å and a density of 0.9176 g cm -3 for P 3 and a = 20.5 Å, c = 28 Å and a density of 0.9241 g cm -3 for P 3c1.