GSAS Parameters & Controls: What to Refine when? (Refinement Recipes)

Presentation Goal

  • Introduce most of the control and refinable parameters in GSAS that are commonly used for powder diffraction (Rietveld analysis). Particular emphasis is made on profile terms, since this is the single most difficult aspect of fitting powder data.
  • Format: PDF slides or a RealPlayer video of the slides with accompanying audio

Presentation Outline

  1. Definitions of terms
  2. Powder peak shapes
    • Fitting functions
    • Size vs. strain broadening
    • Low angle asymmetry
    • Bragg-Brentano issues
  3. GSAS control values
  4. Setting up a refinement
  5. Profile functions and parameter definitions
  6. Preferred orientation
  7. Reducing model complexity (constraints/restraints)
  8. What to refine when (refinement recipe)