Zeolite structure determination from powder diffraction data: applicationsof the FOCUS method

The FOCUS approach to zeolite structure determination from powder diffracti on data has been applied to data from four different zeolitic materials. Th e solutions of the structures of two aluminophosphate molecular sieves, YUL -89 (AWO topology) and YUL-90 (ZON topology), are used to demonstrate routi ne applications of the procedure. The high-silica zeolite ZSM-5 (MFI topolo gy), which has 12 Si atoms (38 framework atoms) in the asymmetric unit, and the gallophosphate cloverite (-CLO topology), the framework of which is no t fully fourfold connected, provide examples of extreme cases, which challe nge the limits of the FOCUS algorithm. Taken together, the four examples gi ve an overview of the practical aspects of the FOCUS method and illustrate its potential and its Limitations.