(4/2)-CONNECTED 3-DIMENSIONAL NETS RELATED TO THE MIXED-COORDINATED FRAMEWORK STRUCTURES ALPO4-15, ALPO4-CJ2 AND ALPO4-12

Application of the same pattern tor linking neighbouring 4.8(2) two-dimensional nets as is found in the AlPO4-CJ2 and AlPO4-15 structures allows the enumeration of eleven (4,2)-connected three-dimensional nets with a maximum unit-cell repeat of approximately 10 angstrom. Net 551 is polytypic with net 398 (the tetrahedral analogue of AlPO4-12). The (4;2)-connected nets related to AlPO4-15 (net 400) and AlPO4-CJ2 (net 725) have the highest symmetry of the present nets. Synthetic zeolite Linde J may have the latter framework topology. Nets 400 and 725 relax considerably upon lowering of the space group symmetry. Geometrical refinements indicate that t e mixed-coordinated AlPO4-15 is more feasible than its (4,2)-connected relative (same space group symmetry), the feasible net 398 and the topologically simpler net 551 have not been observed so far. Geometrically optimized atomic coordinates are given for the most feasible nets obtained here.