Changeset 244

Timestamp:

Dec 4, 2009 5:02:48 PM (13 years ago)

Author:

toby

Message:

# on 2000/07/28 20:16:33, toby did:
document ODF

File:

• trunk/doc/expgui7.html (modified) (2 diffs, 3 props)

trunk/doc/expgui7.html

@@ -30 +30 @@
 The Preferential Orientation Pane is used to control parameters related
 to fitting parameters using the March-Dollase formulation 
-for preferred orientation. In this model one or more axes are designated
+or the spherical harmonic formulation 
+for preferred orientation. Note that GSAS allows both sets of terms to be 
+used at the same time, but it seems unlikely that anyone would 
+actually want to try this.
+
+</DL></DL>
+<h4>A.7.a March-Dollase</H4>
+<DL><DL>
+In this model one or more axes are designated
 as directions [designated by (<i>hkl</i>)] where crystallites are over 
 (Ratio > 1) or underrepresented (Ratio < 1).
@@ -49 +57 @@
 "Off", all terms are displayed for all selected histograms. 
 No attempt is made to group terms or flags.
-<P>
-Note that the other model for treating preferred orientation -- the orientation
-distribution function (spherical harmonics) is not yet implemented
-in EXPGUI and must be accessed from EXPEDT.
+
+</DL></DL>
+<H4>A.7.b Spherical harmonic</H4>
+<DL><DL>
+The spherical harmonic formulation, also referred to as an "orientation
+distribution function" defines a set of terms to treat preferential 
+orientation as a function of the sample symmetry and as a function of
+the Laue phase symmetry of the phase and the selected order expansion. 
+Note that only one set of terms
+is used for each phase, so this function should not be used when the 
+different types of powder data, 
+for example neutron and x-ray data, are used in a single refinement. 
+The setting angles define the orientation of the sample with respect to
+the detectors and are typically used for texture analysis using TOF data
+only.
+
+</DL></DL>
+<img SRC="po3.gif" align=TEXTTOP>
+<DL><DL>
+When more than one phase is present, the phase is selected with the buttons
+in the upper left. Note that 
+when additional terms are added by increasing the spherical harmonic order,
+the new parameters default to zero. Thus, is the order is set to zero
+and then reset to the previous non-zero value, all terms will be
+reset to zero.
+Also, as in EXPEDT, when the sample symmetry is changed, the 
+order is reset to zero.
 </DL></DL>