DIFFaX Modeling of Faulting in the Triclinic Zeolite UZM-55 and Description of a New Polymorph: UZM-55FM

While zeolites are utilized frequently for hydrocarbon conversion and adsorption applications, faulting sometimes creates difficulty in the structural understanding of these materials. We previously reported the idealized structure of UZM-55 and noted some faulting via transmission electron microscopy and electron diffraction experiments. Here, we delineate the fault mode and generate the faulted polymorph model, UZM-55FM. UZM-55FM is also triclinic with the same kinked, one-dimensional pore containing 10-MR and 12-MR delimiting rings but with an AB­(A) stacking sequence rather than an ABC sequence as in the idealized UZM-55 structure. The DIFFaX program was used to model a full range of faulting probabilities after constructing an orthogonal layer and three-dimensional stacking vector, and showed that experimentally synthesized UZM-55 possesses about 20% faulting of a 2-fold type operation on the b axis.