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.