This exercise provides a tutorial example of how to use the GSAS software package with the EXPGUI interface to perform Rietveld analysis. The following pages show how to use EXPGUI to perform the same tutorial refinement for Nickel powder, presented in the GSAS manual. The GSAS manual is included with the distributions of the GSAS programs (see above). The manual can be found EXPGUI website.
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A guide training exercise of quantitative phase analysis using EXPgui_百度文库
These tutorials are intended to be read in parallel with the GSAS manual. Do the following for corundum and repeat later for hydroxyapatite: Unfortunately the fit of the background is not yet acceptable. GSAS General Structure Analysis System is a comprehensive system for the refinement of structural models to both x-ray and neutron diffraction data. Colella De Frede, Napoli Repeat the same for Phase exgui.
Help Center Find new research papers in: It is finally important to remember that these effects can be minimised by reducing the particle size or by using a more penetrating radiation, otherwise they should be corrected using for example the Brindley model.
Executable versions of GSAS are distributed more-or-less freely but the source code is not distributed. Main Menus The File menu allows to save or load a “project” file in which are saved Crystal structures, diffraction data and algorithms Run powpref first and thereafter genles. The glass fraction is then 1 — 0.
Repeat the same for the oxygen atom O at 0. To my experience ,when there is just expgyi preferred orientation direction it is better and safer to use the MD model because the SH model gives a better fit but the physical meaning can be lost if too many coefficients of the polynomial are refined.
Manual – FOX, Free Objects for Crystallography Wiki
The holder was s a 2 mm thick flat Al holder and the data collection was performed using a Philips PW instrument with a conventional Bragg-Brentano BB parafocusing geometry equipped with a copper tube and a secondary beam pyrolitic graphite crystal monochromator.
On the other hand, the peak positions seem fairly good that is the peaks are correctly centred for both phases. Sample selection and preparation The example reported here is a full description of a Rietveld refinement using EXPGUI for the determination of the phase weights in a polyphasic mixture containing an amorphous phase.
See this page on Fox support for CIF import. Three Phase Fault Anal There is a general feeling that the existing models for the correction of microabsorption effects should be revised as they appear to be not adequate even for simple systems containing only crystalline phases Madsen et al.
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One should be very careful with parameter correlations e. There are other codes e.
We are ready for the firt cycles of refinement! The specific problem is usually solved using an internal standard, suitably chosen, which is added in a known amount to the investigated mixture and treated as a mixture component itself.
Further tutorials and information on GSAS can be found on: From the Profile menu, unflag the refined LY and shft parameters. Sometimes you need to reset the profiles to default values if the peakshapes you are refining are too broad.
From the Options menu, first select Auto locate and then Phase 1 for which you will unflag the use of dashed lines and flag the use of show reflections. Structure models can be taken from crystal structure databases such as ICSD see http: Finally click Add atoms.
Remember to change 1 or a couple of things and refine and probably allow only small changes – damping to 8 or 9. The scattering contribution of any amorphous component possibly existing in the sample is a part of the with Mi and Vithe unit cell mass and volume, respectively. As you can see, the fit of the background is still very poor as well as the peak intensities. Site to search This website.