source: trunk/doc/expgui7.html @ 298

Last change on this file since 298 was 298, checked in by toby, 11 years ago

# on 2000/10/03 23:28:06, toby did:
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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<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<h4>A.7.a March-Dollase</H4>
44<DL><DL>
45In this model one or more axes are designated
46as directions [designated by (<i>hkl</i>)] where crystallites are over
47(Ratio > 1) or underrepresented (Ratio < 1).
48The checkbox to the right of the Ratio value determines if it will 
49be refined.
50</DL></DL>
51<img SRC="po1.gif" align=TEXTTOP alt="EXPGUI Screen snapshot">
52<DL><DL>
53If more than one axis is present, one must define the relative fraction
54of preferred orientation for each direction. These fractions are normalized,
55so do not vary the fractions for all directions in a phase.
56</DL></DL>
57<img SRC="po2.gif" align=TEXTTOP alt="EXPGUI Screen snapshot">
58<DL><DL>
59If
60<A href="expgui.html#multiplehistogram">
61"Multiple Histogram Selection" mode</A> is set to any value other than
62"Off", all terms are displayed for all selected histograms.
63No attempt is made to group terms or flags.
64
65</DL></DL>
66<H4>A.7.b Spherical harmonic</H4>
67<DL><DL>
68The spherical harmonic formulation, also referred to as an "orientation
69distribution function" defines a set of terms to treat preferential
70orientation as a function of the sample symmetry and as a function of
71the Laue phase symmetry of the phase and the selected order expansion.
72Note that only one set of terms
73is used for each phase, so this function should not be used when the
74different types of powder data,
75for example neutron and x-ray data, are used in a single refinement.
76The setting angles define the orientation of the sample with respect to
77the detectors and are typically used for texture analysis using TOF data
78only.
79
80</DL></DL>
81<img SRC="po3.gif" align=TEXTTOP  alt="EXPGUI Screen snapshot">
82<DL><DL>
83When more than one phase is present, the phase is selected with the buttons
84in the upper left. Note that
85when additional terms are added by increasing the spherical harmonic order,
86the new parameters default to zero. Thus, is the order is set to zero
87and then reset to the previous non-zero value, all terms will be
88reset to zero.
89Also, as in EXPEDT, when the sample symmetry is changed, the
90order is reset to zero.
91</DL></DL>
92
93<hr>
94<TABLE BORDER BGCOLOR="#FFFF40" ALIGN=RIGHT>
95<TR><TH><A  Href="expgui.html">EXPGUI top</A> 
96</TH><TH><A Href="expguic.html">Menu contents</A>
97</TH><TH><A Href="expgui6.html">Previous page</A>
98</TH></TR></TABLE>
99
100<a href="http://www.ncnr.nist.gov/staff/toby/">Brian Toby</a> (<a href="mailto:brian.toby@nist.gov">Brian.Toby@NIST.GOV</a>)
101<br>
102$Revision: 298 $ $Date: 2009-12-04 23:03:43 +0000 (Fri, 04 Dec 2009) $
103</body>
104</html>
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