A Rietveld-analysis program RIETAN-98 and its applications to zeolites

The latest version of a Rietveld-analysis program, RIETAN-98, for angle-dispersive diffraction has an advanced feature called partial profile relaxation, which means that primary profile parameters of (nearly) isolated reflections can be locally refined independently of secondary profile parameters. This technique was combined with split-type pseudo-Voigt and Pearson VII profile functions to get better fits between observed and calculated patterns. Furthermore, RIETAN-98 has been substantially integrated with a MEED program for a maximum-entropy method (MEM). Visualization of diffraction data by the MEM is very useful for modifying structural models imperfect with respect to positional disorder and various defects. We have been successfully applying RIETAN-98 to various zeolites with guest materials; three representative results of structure refinements will be demonstrated.