| 1 | <html> |
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| 2 | <head> |
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| 3 | <META NAME="Author" CONTENT="Brian H. Toby"> |
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| 4 | <title>EXPGUI Tutorial #7</title> |
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| 5 | </head> |
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| 6 | <BODY BGCOLOR="#FFFFFF"> |
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| 7 | |
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| 8 | <A HREF=http://www.ncnr.nist.gov> |
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| 9 | <IMG SRC="http://www.ncnr.nist.gov/images/ncnrtrans.gif" |
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| 10 | alt="Link to NIST Center for Neutron Research home page" |
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| 11 | ALIGN=RIGHT></A> |
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| 12 | <A HREF=http://www.nist.gov> |
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| 13 | <IMG SRC="http://www.ncnr.nist.gov/images/webidblue_2lineright.gif" |
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| 14 | alt="Link to National Institute of Standards & Technology home page" |
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| 15 | ALIGN=LEFT></A> |
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| 16 | <CENTER> |
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| 17 | <A Href="http://www.ncnr.nist.gov/programs/crystallography/software/tclpkgs.html"> |
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| 18 | <IMG SRC="tcltklogo100.gif" |
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| 19 | alt="Link to Tcl/Tk information"> |
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| 20 | </CENTER></A> |
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| 21 | <hr> |
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| 22 | |
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| 23 | <CENTER> |
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| 24 | <H1>GSAS Nickel example using EXPGUI (part 7)</H1> |
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| 25 | </CENTER> |
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| 26 | <H1> |
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| 27 | 7. Setup for Least-Squares Refinement |
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| 28 | </H1> |
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| 29 | |
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| 30 | Before the model can be refined to better fit the data, the |
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| 31 | structure must be entered. When starting with a new model |
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| 32 | it is a good idea to refine the scale factors for each histogram |
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| 33 | and the background terms before refining any structural parameters. |
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| 34 | So EXPGUI will be used to check which parameters are set to be refined. |
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| 35 | |
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| 36 | <img src="addatom1.gif" align=left> |
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| 37 | First an atom is added to the model by pressing the "Add New Atom" button |
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| 38 | in the lower left of the Phase pane. |
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| 39 | After the atom type, the |
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| 40 | coordinates are added, and the Uiso value is changed, |
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| 41 | press "Add" to add the atom to the .EXP file. |
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| 42 | <BR clear=left><P> |
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| 43 | <img src="addatom2.gif" align=left> |
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| 44 | A box then appears, as shown to the left, to show the results when the atom is read into EXPTOOL. |
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| 45 | <BR clear=left><P> |
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| 46 | <img src="addatom3.gif"> |
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| 47 | <BR clear=left> |
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| 48 | Note that the atom now appears on the phase page. Also note that the cell |
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| 49 | will not be refined, since the "Refine Cell" checkbutton in the upper right |
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| 50 | is not checked. Nor are any atomic parameters being refined, since X V and F |
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| 51 | do not appear in the ref./damp column. |
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| 52 | <BR clear=left> |
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| 53 | <P> |
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| 54 | <img src="bkg1.gif"> |
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| 55 | <BR clear=left> |
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| 56 | We then check each histogram from the Histogram pane, and see that |
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| 57 | the background function has been set to type 4, with 4 terms, as recommended |
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| 58 | in the tutorial, and that no diffractometer constants will be refined |
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| 59 | (above and below). |
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| 60 | <img src="bkg2.gif"> |
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| 61 | <BR clear=left> |
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| 62 | <P> |
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| 63 | <img src="scale1.gif"> |
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| 64 | <BR clear=left> |
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| 65 | We can quickly confirm that the scale factors for the two |
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| 66 | histograms will be refined on the Scaling pane |
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| 67 | (above and below). |
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| 68 | <img src="scale2.gif"> |
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| 69 | <BR clear=left> |
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| 70 | <P> |
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| 71 | <img src="prof1.gif"> |
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| 72 | <BR clear=left> |
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| 73 | Finally we check that no profile terms are being refined on the Profile |
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| 74 | panes. |
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| 75 | (above and below). |
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| 76 | <img src="prof2.gif"> |
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| 77 | <BR clear=left> |
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| 78 | |
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| 79 | <P><BR>(.EXP Snapshot: |
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| 80 | <A HREF="ftp://ftp.ncnr.nist.gov/pub/cryst/gsas/tutorials/nickel7.exp"> |
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| 81 | nickel7.exp |
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| 82 | </A>) |
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| 83 | |
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| 84 | |
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| 85 | <BR clear=left><HR> |
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| 86 | Previous step: <A HREF="nickel6.html"> |
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| 87 | Plot data using POWPLOT or LIVEPLOT</A> |
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| 88 | <BR> |
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| 89 | Next step: <A HREF="nickel8.html"> |
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| 90 | Run GENLES</A> |
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| 91 | |
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| 92 | <BR clear=left> |
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| 93 | <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>) |
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| 94 | <BR clear=left> |
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| 95 | $Revision: 163 $ $Date: 2009-12-04 23:01:27 +0000 (Fri, 04 Dec 2009) $ |
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| 96 | </body> |
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| 97 | </html> |
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