The structure of SSZ-23, the type material of the STT framework type, was reported in 1998 by Camblor et al. In this structure, which has 𝑃2 1 /𝑛 symmetry, the N,N,N-trimethyl-1adamantylammonium (TMAda + ) cations are incorporated in the large, unusually shaped [4 •5 6 •6 5 •7 2 •9 2 ] cavities. The fluoride anions are disordered over three non-equivalent positions in the [4 • ] cages, which have occupancies of 32% (F@Si12), 26% (F@Si13), and 13% (F@Si7), respectively (Figure ). Apart from addition of the OSDA hydrogen atoms and removal of fluoride disorder, no further modifications were made to the experimental structure prior to the DFT calculations (Figure ).