GSAS Tutorial - Moving On

Leslie Struble (University of Illinois) and Paul Stutzman (National Institute of Standards and Technology)

Version 1 (March 2015)

Additional Exercises

Once you have completed these exercises to your satisfaction, you are ready to use the Rietveld method for quantitative X-ray diffraction analysis of portland clinker and cement using data obtained with your diffractometer.

First create an instrument parameter file for your diffractometer. Obtain, prepare, and run a standard single-phase sample of your choosing (corundum, periclase, lime, and quartz are suitable). Using the crystal structure parameters database, refine the crystal structure parameters and the instrument parameters for this pattern.

Unfortunately, GSAS does not transfer refined peak shape parameters when reading from a refined .EXP file, so it is necessary to transfer refined values manually to replicate refined peak shapes from previous refined patterns. This is accomplished by selecting the Profile tab in EXPGUI and editing the peak profile variable values.

Then using the crystal structure parameters provided here and the instrument parameter file for your diffractometer, refine clinker and cement patterns to determine the amount of each phase.

Based on your results with the exercises in these instructions, decide whether or not to use chemical extractions routinely in this analysis.

As you apply this method to your own samples, you will probably develop refinements for crystal structure parameters that provide better fits to the measured data. You can confidently use these refinements as long as you are analyzing samples of a specific chemistry and produced in a specific kiln.