To determine the local interactions between the cages, we used atomistic calculations to investigate the energetics of different packing motifs. We took a single molecule of the cage B11 from the experimentally reported structure (CCDC code PIFVAE) and geometry optimised it using the OPLS4 forcefield, which we have previously shown to perform well at reproducing cage conformations. With the optimised cage, we built dimers of B11 to examine the energetics of the most common packing motifs: window-to-window, windowto-arene, and arene-to-arene. Each dimer was made by displacing a cage along the axis from the centroid of the cage to the centroid of the window or arene facet. To ensure we were exploring adequate configurational phase space for the dimers, we varied: (i) how far away each cage was from its dimer-pair, (ii) the angle of rotation of the cage around the displacement axis, and (iii) the cage's displacement perpendicular to the displacement axis. Details of the full configurational phase space explored are given in Section S1.