While my coffee pot gurgles away here's my tuppence worth As mentioned by previous answers prevention is MUCH better than cure.
Having said that a couple of comments. If there's significant PO then it's a pretty sure thing that the particles are not spherical - so you can forget the Brindley correction which assumes spherical (and also monodisperse BTW) particles. PO is also strongly suggestive (but not certain) of fairly large particles, so microabsorption could be pretty severe. In this case with FeCO3 and Cu radiation microabsorption is going to be an issue independent of whether the PO correction preserves the scale normalization. Pam Dr Pamela Whitfield MRSC CChem Energy Materials Institute for Chemical Process and Environmental Technology (ICPET) Building M12 National Research Council Canada 1200 Montreal Road Ottawa ON K1A 0R6 CANADA Tel: (613) 998-8462 Fax: (613) 991 2384 Email: [EMAIL PROTECTED] -----Original Message----- From: Leonid Solovyov [mailto:[EMAIL PROTECTED] Sent: October 28, 2008 5:53 AM To: Rietveld_l@ill.fr Subject: Re: Quantitative analysis Dear Mario, One more possible problem of applying preferred orientation corrections in QPA is that not all of them are normalized. For example, the March-Dollase correction is normalized and can be applied safely, but the Rietveld-Toraya correction is inapplicable to QPA as it does not preserve the scale normalization. Best regards, Leonid ******************************************************* Leonid A. Solovyov Institute of Chemistry and Chemical Technology K. Marx av., 42 660049, Krasnoyarsk Russia Phone: +7 3912 495663 Fax: +7 3912 238658 www.icct.ru/eng/content/persons/Sol_LA ******************************************************* --- On Mon, 10/27/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: > From: [EMAIL PROTECTED] <[EMAIL PROTECTED]> > Subject: Quantitative analysis > To: Rietveld_l@ill.fr > Date: Monday, October 27, 2008, 3:48 PM > Dear all, > > I have this question, > > I have been refined one mixture (of well-know percentage > composition) of > CaCO3, CaF2, SiO2 and Al2O3, with preferential orientation > in CaCO3 (104) > and CaF2 (111) with good results. When I add to the mixture > FeCO3 and I > refine with preferential orientation (104), it happens that > when I don´t > apply the preferential orientation in all this phases, I > have correct > values of percentage composition, but when I apply the > preferential > orientation the refinement is good but with incorrect > values of percentage > composition. This experiment has been taken in Bragg > Brentano geometry. > How I should refine this mixture? > > Thanks a lot by your help. > > Mario Macías > Universidad Industrial de Santander > Colombia
