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 closer inspection, using the Powplot routine shows the very good fit in a selected region which contains many peaks of both phases Fig.
Since this correction should be the same for both the phases in a homogeneous powder, you have to set an hard contraint so to refine the same value for both the phases.
Write tab will let you write the files in the selected format – txt for Excel and Origin manipulations. EXP does not exist. Click on the Profile menu and change the type of the profile function of both phases Change Type.
You can save a postcript file to print later.
Let the procedure reach convergence. In the main window you can scroll through these patterns by clicking the arrows next to the workspace identifier. LST file which is huge now as it contains all the results of the refinement cycles, check the final weight estimates. For this sample, the powder with average particle size lower than 5? As you can see, the fit of the background is still very poor as well as the peak intensities.
To see the observed and calculated patterns, click on liveplot. Modern Powder Diffraction Rev. Someone may claim this result is ready for publication but if you give a close look at the graphic profiles, you will see that the the fit of the background is still very poor Expvui. More complex systems with their problems of phase identification, chemical substitutions, microabsorption, preferred orientation, excessive peak overlap can only reduce the levels of accuracy and precision that can be attained.
If you get stuck don’t worry about it too much.
Programs (downloads, links and basic instructions)
In the example the first peak of hydroxyapatite if found at about 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.
Click on Edit Background and chose the function type and number of terms. Of Expghi Geology, 28, In the following sections, all the operations to start and run a refinement with EXPGUI are fully described in order to let the reader be able to reproduce the result for the specific example.
Colella De Frede, Napoli Log In Sign Up. If you prefer to save files in an uncompressed manner, you can toggle this behaviour through the Preferences menu.
Repeat the same for Phase 2. Run powpref first and thereafter genles. Run powpref first and genles. Data collection Prior to the quantitative phase analysis one is generally sopposed to have a preliminary qualitative phase analysis in order to determine: Click on the LS Controls menu and put a number of cycles for the refinement I suggest A great one for GSAS is available at: To get the refinement started you need three files: This algorithm is based on the normalisation condition i background and epgui above normalisation equation does not include it.
A guide training exercise of quantitative phase analysis using EXPgui_百度文库
On the other hand, the peak positions seem fairly good that is the peaks are correctly centred for both phases. Do the following for corundum and repeat later for hydroxyapatite: The glass amorphous expvui must be determined indirectly with the aid of an internal standard Gualtieri, Larson and Robert B. The conversion can be achieved using one of the many freeware avialable programs. There are other codes e.
Note the first thing in “name” has to be a letter e. Sometimes you need to reset the profiles to default values if the peakshapes you are refining are too broad.
GSAS General Structure Analysis System is a msnual system for the refinement of structural models to both x-ray and neutron diffraction data. The misfit is large as you will see.