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GSAS Nickel example using EXPGUI (part 5)


Before a least-squares refinement can be run, the POWPREF program must be run. This program assigns the reflections that are associated with each data point in each histogram. For this reason, POWPREF should be rerun if the lattice constants change, if peak widths or asymmetry parameters change or if you change the range of data that you are using in any histogram.

POWPREF can be run in one of three ways. It can be invoked from the menu item in the Powder menu (see to the left), or as a button in the button bar (see below) or by pressing the Alt-P key combination.

Once POWPREF is started, a window is opened to watch the program progress, as is shown above.

Since POWPREF modifies the .EXP file, a message, as shown to the left, is displayed. Pressing "Load new" causes the new .EXP file to be reread. Pressing "Continue editing" causes EXPGUI to continue to edit the previous version of the .EXP file. If more changes are made, and the .EXP file is saved, the changes made by POWPREF will be lost. POWPREF makes only minor changes to the .EXP file, so there is little reason to reject the changes, but if a program, such as GENLES has made many incorrect changes to an experiment, the "Continue editing" option provides an easy way to keep the .EXP file from before the run.

(.EXP Snapshot: nickel5.exp )

Previous step: Change a profile parameter
Next step: Plot data using POWPLOT or LIVEPLOT

Brian Toby (Brian.Toby@NIST.GOV)
$Revision: 161 $ $Date: 2009-12-04 23:01:25 +0000 (Fri, 04 Dec 2009) $