Nr. 8 (2000)


„Rietveld refinement of the crystal structure of sodium-para-hydroxybenzoate using the GSAS program system: a practical guide“


R.E. Dinnebier (Herausgeber – editor)

Inhalt – Table of contents:

1. Introduction to the crystallographic problem
2. Powder X-ray diffraction experiments
3. Program files needed
3.1 The GSAS program system
3.2 The VRML viewer program
3.3 The MATHCAD explorer
4. Input files needed
4.1 NABENZO.GDA: Measured intensities
4.2 NABENZO.BG: Manual background
4.3 X3B1.PAR: Instrument parameter file
4.4 NABENZO.ATO: List of atoms
4.5 NABENZO.MCD: Mathcad file
4.6 NABENZO.EXP: Experiment data file
5. General principles of GSAS
6. The Lebail fit
6.1 Preparing a new experiment file in GSAS
6.2 Run powder data preparation
6.3 Run general least squares
6.4 Refining additional profile parameters
6.5 Refining the zero shift
6.6 Plotting of the refined powder diffraction data
6.7 Wavelength shift
6.8 Anisotropic peak broadening due to micro strain
6.9 Extracting intensities for crystal structure determination
7. The Rietveld fit
7.1 Refining the scale factor only
7.2 Introducing additional atoms
7.3 Fixing the floating origin
7.4 What to do in case of divergence of the refinement
7.5 How to use rigid bodies with satellite groups in GSAS
7.6 How to perform a difference Fourier analysis
7.7 Refining the position of the missing hydroxy-hydrogen atom
7.8 Calculate the R-F and R-F2 values of the refinement
7.9 Switching the soft constraints
8. Description of the structure of Na-para-hydroxybenzoate
8.1 Calculate the bond lengths and angles of the refined structure
8.2 Results and discussion of the crystal structure of Na-para-hydroxybenzoate
8.3 Visualization of the anisotropic strain tensor
9. References