A computational investigation into the effect of extra framework cations on the structural composition of heulandite-type zeolites

The interactions between the extra framework cations, Na(+), K(+) and Ca(2+), and the framework of heulandite-type zeolites have been studied by using atomistic simulation techniques. We have investigated the relationship between the position and type of extra framework cation and the position and number of framework aluminium ions. The results are in good agreement with experiment and suggest that Na(+) ions exert a greater structure-directing role than other ions on the framework silicon/aluminium distribution during synthesis. (C) 1998 Elsevier Science B.V. All rights reserved.