The unit cell parameters of the DFT-optimised AST systems are summarised in Table . When comparing pairs of systems having the same framework composition, but containing different OSDAs, it is worth noting that the incorporation of QNU leads to an expansion of the a axis and a concurrent contraction of the c axis when compared to the corresponding TMA-containing system. Clearly, this is related to the elongated shape of the QNU molecules, which are oriented in a way that the longest molecular dimension lies in the ab plane. Among systems containing the same OSDA, but having different framework composition, replacing elements from the 3 rd period (Si, Al) by elements from the 4 th period leads to an expansion of the unit cell, especially along the c axis, in line with the increase of the atomic radius of the T atoms. Experimental cell parameters are available for three of the eight systems, and the corresponding values are listed in Table .