The answer is in the Rietveld Mailing List archive : http://www.mail-archive.com/rietveld_l...@ill.fr/msg00360.html Friedel pairs are always exactly overlapping in powder diffraction. This is one of the SDPD definite handicaps. Best, Armel Le Bail - Universite du Maine, Laboratoire des Fluorures, CNRS ESA 6010, Av. O. Messiaen, 72085 Le Mans Cedex 9, France http://www.cristal.org/