source: trunk/doc/expgui7.html @ 526

Last change on this file since 526 was 511, checked in by toby, 12 years ago

# on 2001/12/19 18:55:42, toby did:
reformat to match NCNR style

  • Property rcs:author set to toby
  • Property rcs:date set to 2001/12/19 18:55:42
  • Property rcs:lines set to +21 -18
  • Property rcs:rev set to 1.9
  • Property rcs:state set to Exp
  • Property svn:keywords set to Author Date Revision Id
File size: 3.8 KB
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1<html>
2<head>
3   <META NAME="Author" CONTENT="Brian H. Toby">
4   <title>EXPGUI</title>
5   <meta name="keywords" content="crystallography, Rietveld, diffraction,
6   GSAS, EXPGUI">
7</HEAD>
8<style>
9A:link {text-decoration:none}
10A:vlink {text-decoration:none}
11</style>
12
13<BODY BGCOLOR="#FFFFFF"
14      topmargin="0" leftmargin="0" marginwidth="0" marginheight="0" 
15      text="#000000" link="#0033ff" vlink="#0033ff" alink="#0033ff">
16
17<?
18   include("/var/www/include/navigation.inc");
19   include("/var/www/include/utility.inc");
20?>
21<blockquote><font face="arial, helvetica, sans-serif">
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">Next page (Menus)</A>
26</TH><TH><A Href="expgui6.html">Previous page</A>
27</TH></TR></TABLE><BR CLEAR=ALL>
28
29<center><h1>
30<HR noshade width="75%" size="2" align="center">
31EXPGUI, part 7
32<HR noshade width="75%" size="2" align="center">
33</h1></center>
34
35<h3>A.7 Preferential Orientation Pane</h3></a>
36<DL><DL>
37The Preferential Orientation Pane is used to control parameters related
38to fitting parameters using the March-Dollase formulation
39or the spherical harmonic formulation
40for preferred orientation. Note that GSAS allows both sets of terms to be
41used at the same time, but it seems unlikely that anyone would
42actually want to try this.
43
44</DL></DL>
45<a name="MD"></a>
46<h4>A.7.a March-Dollase</H4>
47<DL><DL>
48In this model one or more axes are designated
49as directions [designated by (<i>hkl</i>)] where crystallites are over
50(Ratio > 1) or underrepresented (Ratio < 1).
51The checkbox to the right of the Ratio value determines if it will 
52be refined.
53</DL></DL>
54<img SRC="po1.gif" align=TEXTTOP alt="EXPGUI Screen snapshot">
55<DL><DL>
56If more than one axis is present, one must define the relative fraction
57of preferred orientation for each direction. These fractions are normalized,
58so do not vary the fractions for all directions in a phase.
59</DL></DL>
60<img SRC="po2.gif" align=TEXTTOP alt="EXPGUI Screen snapshot">
61<DL><DL>
62If
63<A href="expgui.html#multiplehistogram">
64"Multiple Histogram Selection" mode</A> is set to any value other than
65"Off", all terms are displayed for all selected histograms.
66No attempt is made to group terms or flags.
67
68</DL></DL>
69<a name="ODF"></a>
70<H4>A.7.b Spherical harmonic</H4>
71<DL><DL>
72The spherical harmonic formulation, also referred to as an "orientation
73distribution function" defines a set of terms to treat preferential
74orientation as a function of the sample symmetry and as a function of
75the Laue phase symmetry of the phase and the selected order expansion.
76Note that only one set of terms
77is used for each phase, so this function should not be used when the
78different types of powder data,
79for example neutron and x-ray data, are used in a single refinement.
80The setting angles define the orientation of the sample with respect to
81the detectors and are typically used for texture analysis using TOF data
82only.
83
84</DL></DL>
85<img SRC="po3.gif" align=TEXTTOP  alt="EXPGUI Screen snapshot">
86<DL><DL>
87When more than one phase is present, the phase is selected with the buttons
88in the upper left. Note that
89when additional terms are added by increasing the spherical harmonic order,
90the new parameters default to zero. Thus, is the order is set to zero
91and then reset to the previous non-zero value, all terms will be
92reset to zero.
93Also, as in EXPEDT, when the sample symmetry is changed, the
94order is reset to zero.
95</DL></DL>
96
97<hr>
98<TABLE BORDER BGCOLOR="#FFFF40" ALIGN=RIGHT>
99<TR><TH><A  Href="expgui.html">EXPGUI top</A> 
100</TH><TH><A Href="expguic.html">Next page (Menus)</A>
101</TH><TH><A Href="expgui6.html">Previous page</A>
102</TH></TR></TABLE>
103
104<a href="http://www.ncnr.nist.gov/staff/toby/">Brian Toby</a> (<a href="mailto:brian.toby@nist.gov">Brian.Toby@NIST.GOV</a>)
105<br>
106$Revision: 511 $ $Date: 2009-12-04 23:07:23 +0000 (Fri, 04 Dec 2009) $
107</blockquote>
108</body>
109</html>
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