source: trunk/doc/expgui7.html @ 337

Last change on this file since 337 was 337, checked in by toby, 11 years ago

# on 2000/10/18 00:11:17, toby did:
fixup formatting

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  • Property rcs:date set to 2000/10/18 00:11:17
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1<html>
2<head>
3   <META NAME="Author" CONTENT="Brian H. Toby">
4   <title>EXPGUI</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<br clear=all><hr>
22
23<TABLE BORDER BGCOLOR="#FFFF40" ALIGN=RIGHT>
24<TR><TH><A  Href="expgui.html">EXPGUI top</A> 
25</TH><TH><A Href="expguic.html">Menu contents</A>
26</TH><TH><A Href="expgui6.html">Previous page</A>
27</TH></TR></TABLE><BR CLEAR=ALL>
28
29<center><h1>
30EXPGUI, part 7
31</h1></center>
32
33<h3>A.7 Preferential Orientation Pane</h3></a>
34<DL><DL>
35The Preferential Orientation Pane is used to control parameters related
36to fitting parameters using the March-Dollase formulation
37or the spherical harmonic formulation
38for preferred orientation. Note that GSAS allows both sets of terms to be
39used at the same time, but it seems unlikely that anyone would
40actually want to try this.
41
42</DL></DL>
43<a name="MD"></a>
44<h4>A.7.a March-Dollase</H4>
45<DL><DL>
46In this model one or more axes are designated
47as directions [designated by (<i>hkl</i>)] where crystallites are over
48(Ratio > 1) or underrepresented (Ratio < 1).
49The checkbox to the right of the Ratio value determines if it will 
50be refined.
51</DL></DL>
52<img SRC="po1.gif" align=TEXTTOP alt="EXPGUI Screen snapshot">
53<DL><DL>
54If more than one axis is present, one must define the relative fraction
55of preferred orientation for each direction. These fractions are normalized,
56so do not vary the fractions for all directions in a phase.
57</DL></DL>
58<img SRC="po2.gif" align=TEXTTOP alt="EXPGUI Screen snapshot">
59<DL><DL>
60If
61<A href="expgui.html#multiplehistogram">
62"Multiple Histogram Selection" mode</A> is set to any value other than
63"Off", all terms are displayed for all selected histograms.
64No attempt is made to group terms or flags.
65
66</DL></DL>
67<a name="ODF"></a>
68<H4>A.7.b Spherical harmonic</H4>
69<DL><DL>
70The spherical harmonic formulation, also referred to as an "orientation
71distribution function" defines a set of terms to treat preferential
72orientation as a function of the sample symmetry and as a function of
73the Laue phase symmetry of the phase and the selected order expansion.
74Note that only one set of terms
75is used for each phase, so this function should not be used when the
76different types of powder data,
77for example neutron and x-ray data, are used in a single refinement.
78The setting angles define the orientation of the sample with respect to
79the detectors and are typically used for texture analysis using TOF data
80only.
81
82</DL></DL>
83<img SRC="po3.gif" align=TEXTTOP  alt="EXPGUI Screen snapshot">
84<DL><DL>
85When more than one phase is present, the phase is selected with the buttons
86in the upper left. Note that
87when additional terms are added by increasing the spherical harmonic order,
88the new parameters default to zero. Thus, is the order is set to zero
89and then reset to the previous non-zero value, all terms will be
90reset to zero.
91Also, as in EXPEDT, when the sample symmetry is changed, the
92order is reset to zero.
93</DL></DL>
94
95<hr>
96<TABLE BORDER BGCOLOR="#FFFF40" ALIGN=RIGHT>
97<TR><TH><A  Href="expgui.html">EXPGUI top</A> 
98</TH><TH><A Href="expguic.html">Menu contents</A>
99</TH><TH><A Href="expgui6.html">Previous page</A>
100</TH></TR></TABLE>
101
102<a href="http://www.ncnr.nist.gov/staff/toby/">Brian Toby</a> (<a href="mailto:brian.toby@nist.gov">Brian.Toby@NIST.GOV</a>)
103<br>
104$Revision: 337 $ $Date: 2009-12-04 23:04:22 +0000 (Fri, 04 Dec 2009) $
105</body>
106</html>
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