I am learning QPA and am worried about PO.
I wonder why sample spinning isn't discussed more. I am luckily able to barrow time on a newer diffractometer with a sample spinner. Does this reduce PO? Or completely eliminate it? There is a set up variable in GSAS for whether you are spinning the sample - are there guidelines for how many revolutions to spin the sample if you just want to reduce PO? Thanks to all for there help!!! Blaise * * * * * * * * * * * * * Blaise Mibeck Research Scientist Energy & Environmental Research Center University of North Dakota 15 North 23rd Street, Stop 9018 Grand Forks, ND 58202-9018 Phone: (701) 777-5077 Email: [EMAIL PROTECTED] -----Original Message----- From: David L. Bish [mailto:[EMAIL PROTECTED] Sent: Tuesday, October 28, 2008 9:09 AM To: Martin; [EMAIL PROTECTED]; rietveld_l@ill.fr Subject: RE: Quantitative analysis I agree that it's always best to avoid preferred orientation, but that is easier said than done on a routine basis. I have personally had good luck with the M-D PO correction on many known samples, as long as the PO was not severe. However, I imagine that Mario's problems are related to microabsorption in this case. Mario, if you can re-measure your data with a Co or Fe tube, it would be a good test of this. Dave Bish At 08:51 AM 10/28/2008 -0400, Martin wrote: Sorry to disagree. Experience tells me otherwise - the March-Dollase correction has nearly always led to poor quant results for me. It most certainly cannot be applied safely. Martin ------------------------------------------ M Vickers Dept of Chemistry UCL ________________________________ > Subject: Re: Quantitative analysis > Date: Tue, 28 Oct 2008 02:53:20 -0700 > From: [EMAIL PROTECTED] > To: Rietveld_l@ill.fr > > 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 > ________________________________ For the best free wallpapers from MSN Click here! <http://wallpapers.msn.com/?ocid>
