Faujasite topology derivation

The Benne11/Schomaker method is not easy to describe and can be illustrated by the first example (see the Appendix) which derives the idealized faujasite topology. The method derives starting x,y,z parameters for the tetrahedral atom of (.125,-.050,.038), which compare with refined parameters of (.125,-.054,.037). The second example derives parameters for the RHO topology of ( A,. 102,. 398) as compared to refined parameters of (%,.1014,.3986). The third example derives idealized parameters for AlPO -16 of (.114,.114,.114) as compared to refined parameters of (.1139,.1139,.1139) and (.1156,.1156,.1156). In these three examples the derived parameters are more than adequate to completely describe the idealized framework topology and can even be used as a starting set in a structure refinement. 

From the topological point of view, with the truncated octahedra of faujasite, a large number of structures can be derived considering a close packing of hexagonal layers of sodalite cages (171. 

Comparison of results. Typical refined tetrahedral atom parameters for a faujasite structure are (0-125,-0-054,0-037), so the parameters derived by the Bennett/Schomaker technique are more than adequate to both build the topology and to be used as a starting set in a refinement. 

---