Dear Madam/Sir(s), I am performing Rietveld analysis for a sample containing perovskites (CaTiO3 and SrTiO3). When putting-in a preferred orientation (PO) correction (100 direction, as the crystals are cubic-like), I obtain better Rwp and GOF i.e. chi-squared values (9.63 and 1.5, respectively) than in the case of not using this correction (Rwp = 10.62 and GOF = 1.65). However, the values of the PO corrections are higher than the errors calculated. All the other parameters including the graphical fit, background etc., seem to be unchanged. I am also convinced about the correctness of any input, with my diffractometer calibrated with LaB6 and Si standards, and Beq / Uiso parameters taken directly from the CIF files provided, so that the microabsorption factor may likely be rejected (?). My guess is that putting in the preferred orientation might artificially, somehow, make the fit better, maybe due to some interdependence?
Could you please kindly suggests if obtaining better statistics (Rwp, GOF) by getting a correction values below the corresponding errors could be treated as a good result? Best regards! -- Łukasz Kruszewski, Ph.D., adjunct Polish Academy of Sciences Institute of Geological Sciences X-Ray Diffraction Laboratory (coordinator) Twarda 51/55 str. 00-818 Warsaw Poland
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