Dear Friedrich, There are inequivalent reflections that overlap even in cubic structures; those where h^2+k^2+l^2 are the same will have identical d-spacings (e.g. 300 & 221, 410 & 322). Check through the list of reflections to see those that have identical d-spacings; these are also listed in the Intl. Tables for X-ray Crystallography Vol II (red book) p 125ff. A LeBail refinement will partition the intensity in some way (probably equally) that is not likely to be what the real ratio is. 2nd point is name given by SHELX to that R-value, wR2, implies some use of a weight. The R(F**2) in GSAS is not weighted. Why this all results in a factor of six; I guess I'm a bit surprised. Best, Bob Von Dreele
R.B. Von Dreele IPNS Division Argonne National Laboratory Argonne, IL 60439-4814 -----Original Message----- From: Friedrich W. Karau [mailto:[EMAIL PROTECTED] Sent: Tuesday, October 17, 2006 9:15 AM To: rietveld_l@ill.fr Subject: R-Value SHELX/GSAS Dear colleagues, may be, that I have comprehension problem. The Bragg R-value is named R(F**2) in GSAS and wR2 in SHELX and defined in the same manner. when I extract the reflexion intesities using a LeBail fit and write them into a hklf6 formatted file, SHELX should refine the structure resulting similar Bragg R-values like GSAS. The fact is, the the R-values obtained by SHELX are about 6 times bigger than the R-values obtained by GSAS. The structure is cubic I, so that no overlap of the reflections occurs apart from the multiplicity, that is incorporated in the hklf6 file. However the structure refines and converges very well in both cases. I have testet refinement with both SHELX and GSAS for a hexagonal structure, too, but the result is the same. The R-values obtained by SHELX are about 6 times bigger than the R-values obtained by GSAS. What could be the reason? Thank you in advance Friedrich ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++ + Friedrich W. Karau email: [EMAIL PROTECTED] + + AK-Schnick Tel.: (+49) (0)89 - 2180-77449 + + LMU - Muenchen mobil: 0179 6647667 + + Department Chemie u. Biochemie Fax: (+49) (0)89 - 2180-77440 + + Butenandtstrasse 5-13(D) URL: www.cup.uni-muenchen.de/ac/schnick + + D-81377 Muenchen + ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ ++++
