source: trunk/tutorial2/garnet4.html @ 171

Last change on this file since 171 was 171, checked in by toby, 11 years ago

# on 2000/05/30 22:22:38, toby did:
Garnet tutorial

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  • Property rcs:date set to 2000/05/30 22:22:38
  • Property rcs:rev set to 1.1
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  • Property svn:keywords set to Author Date Revision Id
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1<html>
2<head>
3   <META NAME="Author" CONTENT="Brian H. Toby">
4   <title>EXPGUI Tutorial #4</title>
5</head>
6<BODY BGCOLOR="#FFFFFF">
7
8<A HREF=http://www.ncnr.nist.gov>
9<IMG SRC="http://www.ncnr.nist.gov/images/ncnrtrans.gif" 
10alt="Link to NIST Center for Neutron Research home page"
11ALIGN=RIGHT></A>
12<A HREF=http://www.nist.gov>
13<IMG SRC="http://www.ncnr.nist.gov/images/webidblue_2lineright.gif" 
14alt="Link to National Institute of Standards & Technology home page"
15ALIGN=LEFT></A>
16<CENTER>
17<A Href="http://www.ncnr.nist.gov/programs/crystallography/software/tclpkgs.html">
18<IMG SRC="tcltklogo100.gif" 
19alt="Link to Tcl/Tk information">
20</CENTER></A>
21<hr>
22
23<CENTER>
24<H1>EXPGUI Tutorial: Garnet (part 4)</H1>
25</CENTER>
26<H1>
274. Run POWPREF and GENLES
28</H1>
29<H3>POWPREF</H3>
30<img src="powpref2.gif" align=left>
31Before a least-squares refinement can be run, the POWPREF program
32must be run. This program assigns the reflections that are associated with
33each data point in each histogram. For this reason, POWPREF should
34be rerun if the lattice constants change, if peak widths or
35asymmetry parameters change or if you change the range of data
36that you are using in any histogram.
37<P>
38POWPREF can be run in one of three ways. It can be invoked from the
39menu item in the Powder menu (see to the left), or as a button in
40the button bar (see below) or by pressing the Alt-P key combination.
41<BR clear=left><P>
42<img src="powpref1a.gif">
43<BR>
44<P>
45<img src="powpref3a.gif">
46<BR>
47<img src="powpref4a.gif" align=left>
48Once POWPREF is started, a window is opened to watch the program
49progress, as is shown above.
50<P>
51Since POWPREF modifies the .EXP file,
52a message, as shown to the left, is displayed.
53Pressing "Load new" causes the new .EXP file to be reread.
54Pressing "Continue editing" causes EXPGUI to continue to edit the
55previous version of the .EXP file. If more changes are made, and
56the .EXP file is saved, the changes made by POWPREF will be lost.
57POWPREF makes only minor changes to the .EXP file, so there
58is little reason to reject the changes, but if a program, such
59as GENLES has made many incorrect changes to an experiment, the
60"Continue editing" option provides an easy way to keep the .EXP file
61from before the run.
62<BR clear=left>
63<P>
64<H3>GENLES</H3>
65At this point it is possible to run GENLES, to fit the initial background
66(three terms) and the scale factor (1 term).
67Similar to how POWPREF was invoked above,
68GENLES can be run from the appropriate
69button on the button bar, by typing Alt-G, or using the GENLES command
70in the Powder or Xtal menus. As soon as GENLES is started, a box appears
71on the screen showing the refinement status. (See below).
72
73<BR clear=left>
74<img src="genles2a.gif">
75
76<BR>
77<img src="powpref4a.gif" align=left>
78When GENLES is finished and the window is
79closed, press "Load new" to cause the revised .EXP
80file to be read. (Pressing "Continue editing" would
81reject the results of the refinement.)
82
83<BR clear=left>
84<P><img src="lstview1.gif">
85
86To examine the results of the refinement in more detail,
87consult the .LST file. This can be examined using the
88LSTVIEW program. This program is shown above. Note that the
89contents of the LSTVIEW box are updated as the refinement
90progresses.
91<P><BR>(.EXP Snapshot:
92<A HREF="ftp://ftp.ncnr.nist.gov/pub/cryst/gsas/tutorials/garnet4.exp">
93garnet4.exp
94</A>)
95
96<BR clear=left><HR>
97Previous step: <A HREF="garnet3.html">
98Add data (histogram) to the Experiment
99</A>
100<BR>
101Next step: <A HREF="garnet5.html">
102Plot data using POWPLOT or LIVEPLOT</A>
103
104<BR clear=left>
105<HR><p><a href="http://www.ncnr.nist.gov/staff/toby/">Brian Toby</a> (<a href="mailto:brian.toby@nist.gov">Brian.Toby@NIST.GOV</a>)
106<BR clear=left>
107$Revision: 171 $ $Date: 2009-12-04 23:01:35 +0000 (Fri, 04 Dec 2009) $
108</body>
109</html>
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