source: trunk/tutorial2/RCS/garnet6.html,v @ 932

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21@Garnet tutorial
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29text
30@<html>
31<head>
32   <title>EXPGUI Tutorial #6</title>
33</head>
34
35<style>
36A:link {text-decoration:none}
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38</style>
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40<BODY BGCOLOR="#FFFFFF"
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44<?
45   include("/var/www/include/navigation.inc");
46   include("/var/www/include/utility.inc");
47?>
48<blockquote>
49
50<CENTER>
51<H1>EXPGUI Tutorial: Garnet (part 6)</H1>
52</CENTER>
53<H1>
546. Additional Least-Squares Refinement
55</H1>
56The initial fit obtained in the previous runs is not particularly good. The
57<A HREF="garnet5.html#diff">"first derivative"</A>
58appearance in the difference plot peaks indicates that
59peaks are not correctly positioned, so refining the lattice parameters and
60zero point correction are the first order of business.
61<BR clear=left><P>
62<img src="fit1.gif">
63<BR clear=left>
64While normally I would recommend refining the lattice first and then
65in a subsequent refinement cycle also refining the zero point correction
66in a later cycle of refinement, with a cubic cell and a small
67zero-point error it is possible to refine both together. Set the refinement
68flag for the lattice (shown above) and the zero point correction (shown below).
69<BR clear=left><P>
70<img src="fit2.gif">
71<BR clear=left><P>
72and then start GENLES, as was done before.
73<BR clear=left><P>
74<img src="fit3.gif">
75<BR clear=left>
76A dramatic improvement is seen both through the agreement factors (above)
77and as seen in the plot (below).
78<BR clear=left><P>
79<a name="ticks"><img src="fit4.gif"></a>
80<BR clear=left><P>
81At this point it is a good idea to run POWPREF and GENLES again,
82since peak positions have moved. This causes the Reduced Chi**2 to drop from
8314.9 to 13.5.
84
85<P><BR>(.EXP Snapshot:
86<A HREF="ftp://ftp.ncnr.nist.gov/pub/cryst/gsas/tutorials/garnet6.exp">
87garnet6.exp
88</A>)
89
90<BR clear=left><HR>
91Previous step: <A HREF="garnet5.html">
92Plot data using POWPLOT or LIVEPLOT</A>
93</A>
94<BR>
95Next step: <A HREF="garnet7.html">
96Define Constraints</A>
97
98<HR>
99</blockquote>
100<P><font size=-1><A HREF="MAILTO:crystal@@NIST.gov?subject=WWW page <?=$PHP_SELF?>">Comments, corrections or questions: crystal@@NIST.gov</A></font><BR>
101<font size=-1><? lastmod(); ?> </font>
102<BR>$Revision: 1.4 $ $Date: 2002/04/12 21:21:18 $
103</body>
104</html>
105@
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107
1081.1
109log
110@Initial revision
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112text
113@a2 1
114   <META NAME="Author" CONTENT="Brian H. Toby">
115a4 1
116<BODY BGCOLOR="#FFFFFF">
117d6 14
118a19 14
119<A HREF=http://www.ncnr.nist.gov>
120<IMG SRC="http://www.ncnr.nist.gov/images/ncnrtrans.gif"
121alt="Link to NIST Center for Neutron Research home page"
122ALIGN=RIGHT></A>
123<A HREF=http://www.nist.gov>
124<IMG SRC="http://www.ncnr.nist.gov/images/webidblue_2lineright.gif"
125alt="Link to National Institute of Standards & Technology home page"
126ALIGN=LEFT></A>
127<CENTER>
128<A Href="http://www.ncnr.nist.gov/programs/crystallography/software/tclpkgs.html">
129<IMG SRC="tcltklogo100.gif"
130alt="Link to Tcl/Tk information">
131</CENTER></A>
132<hr>
133d69 5
134a73 4
135<BR clear=left>
136<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>)
137<BR clear=left>
138$Revision: 1.1 $ $Date: 2000/05/26 16:08:48 $
139@
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