Dear Daxu, You can find this information in GSAS Manual (the file GSAS Manual.pdf is included in the distribution of GSAS and should be available for download from APS web site that is currently not available, at least from my place, I can e-mail it privately if you don´t have it).
In short, both U in Cagliotti's Gaussian FWHM or Y in Lorentzian broadening equations have a behavior with 2theta compatible with strain broadening. You'll need a decent quality powder pattern to refine one or both of the parameters, substract the instrumental contribution to U and/or Y and calculate the sample contribution. But, as the many experts in the list will warn, this is just a simple and possibly inadequate approximation of your sample that should have complexities not necessarily accountable by the model in the software, so care should be taken in making strong assumption based on these numbers. There are other Rietveld refinement software pieces that are devoted to modelling these kind of sample contributions that you may explore. But the results will also depend a lot on your data and the complexity of the sample so you should be careful. Best luck Leo 2016-12-19 9:45 GMT-03:00 Daxu Liu <daxu...@yahoo.com>: > Hi, everyone, > > Someone can supply some information on analyzing strain using GSAS? > Because one of the reviewers asked me to determine the stain of biogenic > calcite, however I don't know how to analyze the refinement data to obtain > the strain. I wonder whether the resolution of conventional Bragg-Brentano > X-ray diffratometer is able to determine the strain. I know GSAS does > describe the strain using some functions for conventional XRPD data. How to > output the corresponding data to calculate the strain. > > > Best regrads, Daxu > > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > Please do NOT attach files to the whole list <alan.he...@neutronoptics.com > > > Send commands to <lists...@ill.fr> eg: HELP as the subject with no body > text > The Rietveld_L list archive is on http://www.mail-archive.com/ > rietveld_l@ill.fr/ > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ > > > -- Dr. Leopoldo Suescun Prof. Agr (Assoc. Prof.) de Física Tel: (+598) 29290705/29249859 Cryssmat-Lab./Cátedra de Fisica/DETEMA Fax: (+598) 29241906* Facultad de Quimica, Universidad de la Republica. Montevideo, Uruguay Ahora la cristalografía importa más (www.iucr.org) Crystallography Matters more.
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++ Please do NOT attach files to the whole list <alan.he...@neutronoptics.com> Send commands to <lists...@ill.fr> eg: HELP as the subject with no body text The Rietveld_L list archive is on http://www.mail-archive.com/rietveld_l@ill.fr/ ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
