I try to refine a powder pattern showing strong peak asymmetry due to 
axial divergence using the approach of Finger, Cox and Jephcoat implemented 
in the GSAS program. The pattern was measured on a conventional diffractometer 
in Bragg-Brentano geometry with Cu K alpha1 radiation ( primary monochromator )
and Soller slits. 
Whenever I try to introduce the S/L and H/L ratios in the calculations the
refinement becomes unstable and diverges. Has anybody gained experience in 
using this asymmetry correction ? Is there someting special to consider ?
Many thanks in advance,
Volker