More recent studies have examined the effect of ionic species which are present in the synthesis mixture of germanosilicate zeolites, namely fluoride ions (F -) and organic structuredirecting agents (OSDAs). It was observed that F -is relatively immobile within D4R units of zeolites AST and ITH and its presence has a significant effect on the relative stabilities of different Ge distributions. Similarly, the presence of the F -/OSDA was found to give rise to larger differences in energy than those due to the choice of germanium distributions. Hence, these species represent an important template for the occupation of D4Rs.