Zeolite structure determination from powder diffraction data: applications of the FOCUS method

The FOCUS approach to zeolite structure determination from powder diffraction data has been applied to data from four different zeolitic materials. The solutions of the structures of two aluminophosphate molecular sieves, YUL-89 (AWO topology) and YUL-90 (ZON topology), are used to demonstrate routine applications of the procedure. The high-silica zeolite ZSM-5 (MFI topology), which has 12 Si atoms (38 framework atoms) in the asymmetric unit, and the gallophosphate cloverite (-CLO topology), the framework of which is not fully fourfold connected, provide examples of extreme cases, which challenge the limits of the FOCUS algorithm. Taken together, the four examples give an overview of the practical aspects of the FOCUS method and illustrate its potential and its limitations.