The fluoride anions in ITQ-4 are incorporated in [4 •5 2 •6 2 ] cages. While pairs of Si atoms at the corners are symmetry-related by the mirror plane in the 𝐼𝑚 structure, this is no longer the case in the fully ordered 𝑃𝑛 structure. 10 of the 12 vertices of the cage correspond to meeting points of three edges, and all these fluoride positions were considered in the optimizations. The results are summarized in Figure . One of the experimental sites (F@Si6_1) is lowest in energy, and there is a clear energetic preference for positions associated with the four-membered rings.