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Date: Mon, 12 Feb 2001 14:01:07 -0800 (PST) Subject: X Ray diffraction From: CHANDRASEN RATHOR [chandrasen11@yahoo.com] Respected Members, I have some queries regarding X ray diffraction analysis and modern techniques. 1)can we calculate dislocation density from X ray diffraction? If yes please explain in briefly . 2)If we can measure dislocation densities then can we quantify by X ray diffraction? I will be very thankful for your further comments. Thanks Chandra.

Date: Tue, 13 Feb 2001 01:06:22 +0100 To: rietveld_l@ill.fr From: Armel Le Bail [armel@fluo.univ-lemans.fr] Subject: Re: X Ray diffraction >1)can we calculate dislocation density from X ray >diffraction? You mean by the Rietveld method ? Well, some formula are the same for any kind of dislocation. This should raise some doubt about their validity. So, I would briefly answer, concerning these formula : No. But contrary opinions are also circulating. No real consensus. See the book : http://www.oup.co.uk/isbn/0-19-850189-7 and go to that future conference : http://bragg.ing.unitn.it/sizestrain/ Best wishes, Armel Le Bail http://www.cristal.org/

Date: Wed, 14 Feb 2001 09:20:31 +0100 To: rietveld_l@ill.fr From: Jean-Marc Joubert [jean-marc.joubert@glvt-cnrs.fr] Subject: Re: X Ray diffraction At , you wrote: >Respected Members, > >I have some queries regarding X ray diffraction >analysis and modern >techniques. > >1)can we calculate dislocation density from X ray >diffraction? If yes please explain in briefly . > >2)If we can measure dislocation densities then can we >quantify by X ray diffraction? > Theories by Krivoglaz (Theory of X-ray and thermal neutron scattering by real crystals, (1969), New-York: Plenum) are linking strain line broadening to dislocation densities. Formulas have been derived, for example in the case of the hexagonal structure (Klimanek and Kuzel, J. Appl. Crystallogr. 21 (1988) 59-66, 21 (1988) 363-368, 22 (1989) 299-307) and applied to the case of hydrided-dehydrided Pd (cubic) or LaNi5 type materials (hexagonal) (Wu et al, J. Appl. Crystallogr. 31 (1998) 356-362, 363-368, Cerny and Joubert, J. Appl. Crystallogr. 33 (2000) 997-1005). The latter compounds show very high anisotropic line broadening exclusively due to dislocation density. The analysis allow the determination of the slip system involved and the measurement of the dislocation density. ------------------------------------ Jean-Marc Joubert Chargé de recherche Laboratoire de Chimie Métallurgique des Terres Rares CNRS - UPR 209 2 - 8 rue Henri Dunant - 94320 THIAIS Cedex - FRANCE phone : 33 1 49 78 12 11 fax : 33 1 49 78 12 03 email : jean-marc.joubert@glvt-cnrs.fr web : http://www.glvt-cnrs.fr/lcmtr/