EXPGUI Tutorial: Garnet (Intro)

Introduction

The following pages show how to use EXPGUI to perform the same tutorial refinement for Yttrium Iron Garnet powder, presented in the GSAS manual (pages 65-81 in the 9/1/94 edition) but using EXPGUI instead of EXPEDT, as done in the manual.

Note:

while it is possible to have your working GSAS files (for example the .EXP file) in a separate directory from the raw data file(s), I discourage this practice as it then becomes quite difficult to later copy or move the .EXP file from one directory or computer to another. For this reason, I suggest copying the data (.RAW) files into the directory where you will create the Experiment (.EXP) file.

For this example, I am working in directory /home/toby/work, and the data files and parameters files are in directory /home/toby/gsas/example, so I copy the Garnet data and instrument parameter file using UNIX commands:

       cp /home/toby/gsas/example/garnet.raw   /home/toby/work/
       cp /home/toby/gsas/example/inst_d1a.prm /home/toby/work/

For Windows I would likely copy the files by dragging their icons between the appropriate folders.

Tutorial Outline

1. Creating a GSAS Experiment File
2. Add a phase and atoms to the Experiment
3. Add data (histogram) to the Experiment
4. Run POWPREF and GENLES
5. Plot data using POWPLOT or LIVEPLOT
6. Additional Least-Squares Refinement
7. Define constraints
8. Vary atomic parameters
9. Compute Bond Distances and Angles

• Other notes (includes RAWPLOT example)

Sample files

Sample .EXP files have been saved at points through the tutorial. These are indicated in the tutorial as ".EXP snapshots". These files have been reformatted for DOS/Windows, but EXPGUI users will have no trouble using them on either platform.

• garnet2.exp -- After adding a phase and atoms to the Experiment
• garnet3.exp -- After adding data (histograms) to the Experiment
• garnet4.exp -- After initial GENLES
• garnet6.exp -- After fitting cell and zero point
• garnet7.exp -- After defining constraints
• garnet8.exp -- After final refinement

Other sample files:

• garnet.raw -- data file
• inst_d1a.prm -- instrument parameter file

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Comments, corrections or questions: crystal@NIST.gov
Last modified 18-July-2003
$Revision: 1.4 $ $Date: 2003/07/18 18:33:10 $