| 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 #5</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 5)</H1> |
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| 25 | </CENTER> |
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| 26 | <H1> |
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| 27 | 5. Run POWPREF |
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| 28 | </H1> |
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| 29 | <img src="powpref2.gif" align=left> |
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| 30 | Before a least-squares refinement can be run, the POWPREF program |
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| 31 | must be run. This program assigns the reflections that are associated with |
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| 32 | each data point in each histogram. For this reason, POWPREF should |
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| 33 | be rerun if the lattice constants change, if peak widths or |
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| 34 | asymmetry parameters change or if you change the range of data |
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| 35 | that you are using in any histogram. |
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| 36 | <P> |
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| 37 | POWPREF can be run in one of three ways. It can be invoked from the |
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| 38 | menu item in the Powder menu (see to the left), or as a button in |
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| 39 | the button bar (see below) or by pressing the Alt-P key combination. |
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| 40 | <BR clear=left><P> |
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| 41 | <img src="powpref1.gif"> |
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| 42 | <BR> |
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| 43 | <P> |
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| 44 | <img src="powpref3.gif"> |
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| 45 | <BR> |
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| 46 | <img src="powpref4.gif" align=left> |
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| 47 | Once POWPREF is started, a window is opened to watch the program |
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| 48 | progress, as is shown above. |
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| 49 | <P> |
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| 50 | The exact behavior of the window after the run completes is somewhat |
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| 51 | system-dependent. In Windows-95 and UNIX you must press the "Enter" or |
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| 52 | "Return" key for the run to complete, but in Windows-NT this is not |
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| 53 | the case. For both versions of Windows, you may or may not need to |
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| 54 | close the window manually once the run is complete, depending on your |
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| 55 | system's settings. |
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| 56 | <P> |
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| 57 | Every time that EXPGUI detects that a change has been made in the .EXP file |
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| 58 | by another program (in this case by POWPREF) this message appears to offer |
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| 59 | to choices: to continue using the previously read file or to reload the |
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| 60 | changed file. If you press the "Continue editing" button, EXPGUI will |
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| 61 | ignore the changes in the .EXP file made by POWPREF, but if you press |
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| 62 | the "Load new", these changes are read and accepted. |
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| 63 | <P> |
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| 64 | In this case press |
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| 65 | "Load new" to use the results of POWPREF. However if a program |
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| 66 | makes changes to the .EXP file that you do not like |
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| 67 | (this is most common with GENLES, when a refinement diverges) |
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| 68 | you can reject the changes by pressing "Continue editing." When the |
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| 69 | .EXP file is later changes and saved, it will overwrite the results in |
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| 70 | the rejected run. |
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| 71 | |
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| 72 | <P><BR>(.EXP Snapshot: |
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| 73 | <A HREF="ftp://ftp.ncnr.nist.gov/pub/cryst/gsas/tutorials/nickel5.exp"> |
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| 74 | nickel5.exp |
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| 75 | </A>) |
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| 76 | |
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| 77 | <BR clear=left><HR> |
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| 78 | Previous step: <A HREF="nickel4.html"> |
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| 79 | Change a profile parameter |
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| 80 | </A> |
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| 81 | <BR> |
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| 82 | Next step: <A HREF="nickel6.html"> |
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| 83 | Plot data using POWPLOT or LIVEPLOT</A> |
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| 84 | |
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| 85 | <BR clear=left> |
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| 86 | <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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| 87 | <BR clear=left> |
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| 88 | $Revision: 208 $ $Date: 2009-12-04 23:02:12 +0000 (Fri, 04 Dec 2009) $ |
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| 89 | </body> |
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| 90 | </html> |
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