Changeset 1661


Ignore:
Timestamp:
Feb 18, 2015 1:23:30 PM (8 years ago)
Author:
vondreele
Message:

modified calibration tutorial

Location:
Tutorials/TOF Calibration
Files:
6 edited

Legend:

Unmodified
Added
Removed

  • Tutorials/TOF Calibration/Calibration of a TOF powder diffractometer.htm

    r1651 r1661  
    2525  <o:Author>Von Dreele</o:Author>
    2626  <o:LastAuthor>Von Dreele</o:LastAuthor>
    27   <o:Revision>2</o:Revision>
    28   <o:TotalTime>409</o:TotalTime>
     27  <o:Revision>4</o:Revision>
     28  <o:TotalTime>672</o:TotalTime>
    2929  <o:Created>2015-02-12T20:52:00Z</o:Created>
    30   <o:LastSaved>2015-02-12T20:52:00Z</o:LastSaved>
     30  <o:LastSaved>2015-02-18T19:20:00Z</o:LastSaved>
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    3434  <o:Company>Argonne National Laboratory</o:Company>
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    11291135<p class=MsoNormal>In this tutorial, data collected on the SNS instrument
    11301136POWGEN, are used. The calibration process will use the fitted positions of all
    1131 visible peaks in a pattern of NIST SRM 660b La<sup>10</sup>B<sub>6</sub>
    1132 (a=4.15689Å) obtained in a multiple single peak fit. The positions will be
    1133 compared to those expected from the known lattice parameters to establish the
    1134 diffractometer constants (difC, difA, difB and Zero) used for calculating TOF
    1135 peak positions from d-spacings. Note that menu entries are listed in bold face
    1136 below as <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1137 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:
    1138 Calibri;mso-bidi-theme-font:minor-latin'>Help/About GSAS-II</span></b>, which
    1139 lists first the name of the menu (here <b style='mso-bidi-font-weight:normal'><span
     1137visible peaks in a pattern of NIST SRM 660b La<sup>10</sup>B<sub>6</sub> (a=4.15689Å)
     1138obtained in a multiple single peak fit. The positions will be compared to those
     1139expected from the known lattice parameters to establish the diffractometer
     1140constants (<span class=SpellE>difC</span>, <span class=SpellE>difA</span>, <span
     1141class=SpellE>difB</span> and Zero) used for calculating TOF peak positions from
     1142d-<span class=SpellE>spacings</span>. For the second part of this tutorial, the
     1143suite of peaks will be extended to include every visible peak in the pattern
     1144and the peak fitting will include the various profile coefficients thus fully
     1145describing the instrument contribution to the peak profiles. Note that menu
     1146entries and user input are shown in bold face below as <b style='mso-bidi-font-weight:
     1147normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     1148minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:Calibri;
     1149mso-bidi-theme-font:minor-latin'>Help/About GSAS-II</span></b>, which lists
     1150first the name of the menu (here <b style='mso-bidi-font-weight:normal'><span
    11401151style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
    11411152mso-hansi-theme-font:minor-latin;mso-bidi-font-family:Calibri;mso-bidi-theme-font:
    … …  
    11481159href="Starting%20GSAS.htm"><span style='color:windowtext;text-decoration:none;
    11491160text-underline:none'>start GSAS-II</span></a></span></u>.</p>
     1161
     1162<h1>Part I. Determine the diffractometer constants</h1>
    11501163
    11511164<h2>Step 1: Read in the data file</h2>
    … …  
    11811194mso-hansi-theme-font:minor-latin;mso-no-proof:yes'>PGHR_60-2015A.prm</span></b><span
    11821195style='mso-no-proof:yes'> file. It contains the POWGEN instrument parameters
    1183 provided along with the data. <o:p></o:p></span></p>
     1196provided along with the data; this file is in the old GSAS iparm file format
     1197and does not include all the instrument parameters used by GSAS-II. This is
     1198what we will be improving in this tutorial.<o:p></o:p></span></p>
    11841199
    11851200<p class=MsoNormal><span style='mso-no-proof:yes'><o:p>&nbsp;</o:p></span></p>
    … …  
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    12091224 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image001.png"
    … …  
    12261241<p class=MsoNormal><b style='mso-bidi-font-weight:normal'><span
    12271242style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape id="Picture_x0020_16"
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    12301245 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image002.png"
    … …  
    12451260Select the menu item <b style='mso-bidi-font-weight:normal'><span
    12461261style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
    1247 mso-hansi-theme-font:minor-latin'>Peak Fitting/Auto search</span></b> to populate
    1248 the <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1249 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Peak List</span></b>.
    1250 This will select almost every peak in the pattern.</p>
    1251 
    1252 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1253  id="Picture_x0020_17" o:spid="_x0000_i1039" type="#_x0000_t75" style='width:466.5pt;
     1262mso-hansi-theme-font:minor-latin'>Peak Fitting/Auto search</span></b> to
     1263populate the <b style='mso-bidi-font-weight:normal'><span style='font-family:
     1264"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:
     1265minor-latin'>Peak List</span></b>. This will select almost every peak in the
     1266pattern (I got 66 peaks).</p>
     1267
     1268<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1269 id="Picture_x0020_17" o:spid="_x0000_i1055" type="#_x0000_t75" style='width:466.5pt;
    12541270 height:399.75pt;visibility:visible;mso-wrap-style:square'>
    12551271 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image004.png"
    … …  
    12601276
    12611277<p class=MsoNormal>However, it can fail by selecting a peak multiple times if
    1262 the data is sufficiently noisy. You should check through the list and eliminate
    1263 any close duplicates (in this instance there didn’t appear to be any). A peak
    1264 can be eliminated by placing the cursor on the vertical blue line and pressing
    1265 the right mouse button; the line should vanish and the entry in the table
    1266 deleted. Notice that the position for the highest TOF peak is misplaced. You
    1267 can shift it by placing the cursor on the blue line and with the left mouse
    1268 button down, drag the line to match the peak top (zooming in before can help).
    1269 If you want you can add more of the unpicked lines to the list (I didn’t). To
    1270 do this (zooming in helps) place the cursor on a data point at the top of a
    1271 peak and press the left mouse button. It is easiest to proceed from right to
    1272 left so the tool tip stays out of the way as you work. For any of these
    1273 operations the zoom buttons at the bottom left of the plot window must be
    1274 turned off (NB: one is turned on in the above plot).</p>
     1278the data is too noisy. You should check through the list and eliminate any
     1279close duplicates (in this instance there didn’t appear to be any). A peak can
     1280be eliminated by placing the cursor on the vertical blue line and pressing the
     1281right mouse button; the line should vanish and the entry in the table deleted.
     1282Notice that the position for the highest TOF peak is misplaced. You can shift
     1283it by placing the cursor on the blue line and with the left mouse button down,
     1284drag the line to match the peak top (zooming in before can help). If you want
     1285you can add more of the unpicked lines to the list (I didn’t). To do this
     1286(zooming in helps) place the cursor on a data point at the top of a peak and
     1287press the left mouse button. It is easiest to proceed from right to left so the
     1288tool tip stays out of the way as you work. For any of these operations the zoom
     1289buttons at the bottom left of the plot window must be turned off (NB: one is
     1290turned on in the above plot).</p>
    12751291
    12761292<h2>Step 3: Fit peaks</h2>
    … …  
    12781294<p class=MsoNormal>To do the initial fit to the peaks, select the <b
    12791295style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1280 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Peak
    1281 Fitting/Peakfit</span></b> menu item in the <b style='mso-bidi-font-weight:
     1296mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Peak Fitting/<span
     1297class=SpellE>Peakfit</span></span></b> menu item in the <b style='mso-bidi-font-weight:
    12821298normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
    12831299minor-latin;mso-hansi-theme-font:minor-latin'>Peak List</span></b> data window.
    … …  
    12851301style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    12861302mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>calibrate</span></b>).
    1287 The project file (<b style='mso-bidi-font-weight:normal'><span
    1288 style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
    1289 mso-hansi-theme-font:minor-latin'>calibrate.gpx</span></b>) will be written
    1290 into your local directory selected in the File Dialog; then the refinement will
    1291 proceed. The resulting plot will look like (I keyed ‘<b style='mso-bidi-font-weight:
     1303The project file (<span class=SpellE><b style='mso-bidi-font-weight:normal'><span
     1304style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1305mso-hansi-theme-font:minor-latin'>calibrate.gpx</span></b></span>) will be
     1306written into your local directory selected in the File Dialog; then the refinement
     1307will proceed. The resulting plot will look like (I keyed ‘<b style='mso-bidi-font-weight:
    12921308normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
    12931309minor-latin;mso-hansi-theme-font:minor-latin'>s</span></b>’ and ‘<b
    12941310style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    12951311mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>q</span></b>’
    1296 on the plot to get a sqrt(I) vs q plot which spread out the peaks a bit better
    1297 than a I vs TOF plot).</p>
    1298 
    1299 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1300  id="Picture_x0020_18" o:spid="_x0000_i1038" type="#_x0000_t75" style='width:525pt;
    1301  height:450pt;visibility:visible;mso-wrap-style:square'>
     1312on the plot to get a <span class=SpellE>sqrt</span>(I) vs q plot which spread
     1313out the peaks a bit better than a I vs TOF plot).</p>
     1314
     1315<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1316 id="_x0000_i1054" type="#_x0000_t75" style='width:525pt;height:450pt;
     1317 visibility:visible;mso-wrap-style:square'>
    13021318 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image006.png"
    13031319  o:title=""/>
    13041320</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
    13051321src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image006.png"
    1306 v:shapes="Picture_x0020_18"><![endif]></span></p>
     1322v:shapes="_x0000_i1054"><![endif]></span></p>
    13071323
    13081324<p class=MsoNormal>The fit to the background can be improved by adding more
    1309 terms; I set the number of chebyschev terms to <b style='mso-bidi-font-weight:
    1310 normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
    1311 minor-latin;mso-hansi-theme-font:minor-latin'>6</span></b>. The peak positions
    1312 should also be refined; to set them go back to the <b style='mso-bidi-font-weight:
    1313 normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
    1314 minor-latin;mso-hansi-theme-font:minor-latin'>Peak List</span></b> data window,
    1315 select one of the items under the 1<sup>st</sup> <b style='mso-bidi-font-weight:
    1316 normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
    1317 minor-latin;mso-hansi-theme-font:minor-latin'>refine</span></b> column, select
    1318 the “<b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1319 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>refine</span></b>”
    1320 box (the column will turn blue), then press ‘y. All the position refine boxes
     1325terms; I set the number of <span class=SpellE>chebyschev</span> terms to <b
     1326style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1327mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>6</span></b>.
     1328The peak positions should also be refined; to set them go back to the <b
     1329style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1330mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Peak List</span></b>
     1331data window, select one of the items under the 1<sup>st</sup> <b
     1332style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1333mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>refine</span></b>
     1334column, select the “<b style='mso-bidi-font-weight:normal'><span
     1335style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1336mso-hansi-theme-font:minor-latin'>refine</span></b>” box (the column will turn
     1337blue), then press <b style='mso-bidi-font-weight:normal'><span
     1338style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1339mso-hansi-theme-font:minor-latin'>y</span></b>. All the position refine boxes
    13211340will be checked. Then repeat the <b style='mso-bidi-font-weight:normal'><span
    13221341style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
    1323 mso-hansi-theme-font:minor-latin'>Peak Fitting/Peakfit</span></b> menu item; a
    1324 new plot will appear with a better fit.</p>
    1325 
    1326 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1327  id="Picture_x0020_19" o:spid="_x0000_i1037" type="#_x0000_t75" style='width:525pt;
    1328  height:450pt;visibility:visible;mso-wrap-style:square'>
     1342mso-hansi-theme-font:minor-latin'>Peak Fitting/<span class=SpellE>Peakfit</span></span></b>
     1343menu item; a new plot will appear with a better fit.</p>
     1344
     1345<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1346 id="_x0000_i1053" type="#_x0000_t75" style='width:525pt;height:450pt;
     1347 visibility:visible;mso-wrap-style:square'>
    13291348 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image007.png"
    13301349  o:title=""/>
    13311350</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
    13321351src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image007.png"
    1333 v:shapes="Picture_x0020_19"><![endif]></span></p>
     1352v:shapes="_x0000_i1053"><![endif]></span></p>
    13341353
    13351354<h2>Step 4: Setup for calibration</h2>
    … …  
    13441363mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Operations/Load/Reload</span></b>
    13451364menu item. The data table will show the positions &amp; intensities along with
    1346 0,0,0 for h,k,l for each one.</p>
    1347 
    1348 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1349  id="Picture_x0020_20" o:spid="_x0000_i1036" type="#_x0000_t75" style='width:367.5pt;
    1350  height:225pt;visibility:visible;mso-wrap-style:square'>
     1365000 for <span class=SpellE>hkl</span> for each one.</p>
     1366
     1367<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1368 id="_x0000_i1052" type="#_x0000_t75" style='width:367.5pt;height:225pt;
     1369 visibility:visible;mso-wrap-style:square'>
    13511370 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image008.png"
    13521371  o:title=""/>
    13531372</v:shape><![endif]--><![if !vml]><img border=0 width=490 height=300
    13541373src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image008.png"
    1355 v:shapes="Picture_x0020_20"><![endif]></span></p>
     1374v:shapes="_x0000_i1052"><![endif]></span></p>
    13561375
    13571376<p class=MsoNormal>Next, select the <b style='mso-bidi-font-weight:normal'><span
    13581377style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
    13591378mso-hansi-theme-font:minor-latin'>Unit Cells List</span></b> from the GSAS-II
    1360 Data tree. A new window will appear. Change Bravais lattice to <b
    1361 style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1362 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Pm3m</span></b>,
    1363 select <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1364 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>P m 3 m</span></b>
    1365 for the Space group and enter the lattice parameter (<b style='mso-bidi-font-weight:
    1366 normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
    1367 minor-latin;mso-hansi-theme-font:minor-latin'>4.15689</span></b>) in the <b
     1379Data tree. A new window will appear. Change <span class=SpellE>Bravais</span>
     1380lattice to <b style='mso-bidi-font-weight:normal'><span style='font-family:
     1381"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:
     1382minor-latin'>Pm3m</span></b>, select <b style='mso-bidi-font-weight:normal'><span
     1383style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1384mso-hansi-theme-font:minor-latin'>P m 3 m</span></b> for the Space group and
     1385enter the lattice parameter (<b style='mso-bidi-font-weight:normal'><span
     1386style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1387mso-hansi-theme-font:minor-latin'>4.15689</span></b>) in the <b
    13681388style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    13691389mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Unit cell: a
    1370 =</span></b> box. The window should look like</p>
    1371 
    1372 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1373  id="Picture_x0020_21" o:spid="_x0000_i1035" type="#_x0000_t75" style='width:546pt;
    1374  height:184.5pt;visibility:visible;mso-wrap-style:square'>
     1390=</span></b> box (Press <b style='mso-bidi-font-weight:normal'><span
     1391style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1392mso-hansi-theme-font:minor-latin'>Enter</span></b> to set the value). The
     1393window should look like</p>
     1394
     1395<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1396 id="_x0000_i1051" type="#_x0000_t75" style='width:546pt;height:184.5pt;
     1397 visibility:visible;mso-wrap-style:square'>
    13751398 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image009.png"
    13761399  o:title=""/>
    13771400</v:shape><![endif]--><![if !vml]><img border=0 width=728 height=246
    13781401src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image009.png"
    1379 v:shapes="Picture_x0020_21"><![endif]></span></p>
     1402v:shapes="_x0000_i1051"><![endif]></span></p>
    13801403
    13811404<p class=MsoNormal>Press the <b style='mso-bidi-font-weight:normal'><span
    13821405style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
    1383 mso-hansi-theme-font:minor-latin'>Show hkl positions</span></b> button, the
    1384 plot should show a suite of red dashed vertical lines giving all the allowed
    1385 reflection positions which should closely match the blue peak position lines.</p>
    1386 
    1387 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1388  id="Picture_x0020_23" o:spid="_x0000_i1034" type="#_x0000_t75" style='width:560.25pt;
     1406mso-hansi-theme-font:minor-latin'>Show <span class=SpellE>hkl</span> positions</span></b>
     1407button, the plot should show a suite of red dashed vertical lines giving all
     1408the allowed reflection positions which should closely match the blue peak position
     1409lines.</p>
     1410
     1411<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1412 id="Picture_x0020_23" o:spid="_x0000_i1050" type="#_x0000_t75" style='width:560.25pt;
    13891413 height:450pt;visibility:visible;mso-wrap-style:square'>
    13901414 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image010.png"
    … …  
    13941418v:shapes="Picture_x0020_23"><![endif]></span></p>
    13951419
    1396 <p class=MsoNormal>The Index Peak List window now shows hkl values for each
    1397 entry</p>
    1398 
    1399 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1400  id="Picture_x0020_24" o:spid="_x0000_i1033" type="#_x0000_t75" style='width:367.5pt;
     1420<p class=MsoNormal>The Index Peak List window now shows <span class=SpellE>hkl</span>
     1421values for each entry</p>
     1422
     1423<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1424 id="Picture_x0020_24" o:spid="_x0000_i1049" type="#_x0000_t75" style='width:367.5pt;
    14011425 height:225pt;visibility:visible;mso-wrap-style:square'>
    14021426 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image011.png"
    … …  
    14111435
    14121436<p class=MsoNormal>As we now have a set of reflection positions each properly
    1413 indexed so that the d-spacings are known, we can now determine the
    1414 diffractometer coefficients (C, A, B and Z) that give TOF from d-spacing
    1415 according to</p>
     1437indexed so that the d-<span class=SpellE>spacings</span> are known, we can now
     1438determine the diffractometer coefficients (C, A, B and Z) that give TOF from
     1439d-spacing according to</p>
    14161440
    14171441<p class=MsoNormal><o:p>&nbsp;</o:p></p>
    … …  
    14361460mso-fareast-language:EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape
    14371461 id="_x0000_i1025" type="#_x0000_t75" style='width:2in;height:18.75pt'>
    1438  <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image012.png"
     1462 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image022.png"
    14391463  o:title="" chromakey="white"/>
    14401464</v:shape><![endif]--><![if !vml]><img width=192 height=25
    1441 src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image013.png"
     1465src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image018.png"
    14421466v:shapes="_x0000_i1025"><![endif]></span><![endif]></p>
    14431467
    … …  
    14501474
    14511475<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1452  id="Picture_x0020_25" o:spid="_x0000_i1032" type="#_x0000_t75" style='width:411pt;
    1453  height:220.5pt;visibility:visible;mso-wrap-style:square'>
     1476 id="_x0000_i1048" type="#_x0000_t75" style='width:411pt;height:220.5pt;
     1477 visibility:visible;mso-wrap-style:square'>
    14541478 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image014.png"
    14551479  o:title=""/>
    14561480</v:shape><![endif]--><![if !vml]><img border=0 width=548 height=294
    14571481src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image014.png"
    1458 v:shapes="Picture_x0020_25"><![endif]></span></p>
     1482v:shapes="_x0000_i1048"><![endif]></span></p>
    14591483
    14601484<p class=MsoNormal>And the plot will show the corresponding function curves </p>
    14611485
    14621486<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1463  id="Picture_x0020_26" o:spid="_x0000_i1031" type="#_x0000_t75" style='width:560.25pt;
     1487 id="Picture_x0020_26" o:spid="_x0000_i1047" type="#_x0000_t75" style='width:560.25pt;
    14641488 height:450pt;visibility:visible;mso-wrap-style:square'>
    14651489 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image015.png"
    … …  
    14691493v:shapes="Picture_x0020_26"><![endif]></span></p>
    14701494
    1471 <p class=MsoNormal>Although a previous calibration gave values for difA and
    1472 Zero, we will start fresh; set them both to zero. Select the <b
    1473 style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1474 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>difC Refine</span></b>?
    1475 box and do <b style='mso-bidi-font-weight:normal'><span style='font-family:
    1476 "Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:
    1477 minor-latin'>Operations/Calibrate</span></b>; the plot will show the result of
    1478 the calibration</p>
    1479 
    1480 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1481  id="Picture_x0020_27" o:spid="_x0000_i1030" type="#_x0000_t75" style='width:560.25pt;
    1482  height:450pt;visibility:visible;mso-wrap-style:square'>
     1495<p class=MsoNormal>Although a previous calibration gave values for <span
     1496class=SpellE>difA</span> and Zero, we will start fresh; set them both to zero.
     1497Select the <span class=SpellE><b style='mso-bidi-font-weight:normal'><span
     1498style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1499mso-hansi-theme-font:minor-latin'>difC</span></b></span><b style='mso-bidi-font-weight:
     1500normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     1501minor-latin;mso-hansi-theme-font:minor-latin'> <span class=GramE>Refine</span></span></b>?
     1502<span class=GramE>box</span> and do <b style='mso-bidi-font-weight:normal'><span
     1503style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1504mso-hansi-theme-font:minor-latin'>Operations/Calibrate</span></b>; the plot
     1505will show the result of the calibration</p>
     1506
     1507<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1508 id="_x0000_i1046" type="#_x0000_t75" style='width:560.25pt;height:450pt;
     1509 visibility:visible;mso-wrap-style:square'>
    14831510 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image016.png"
    14841511  o:title=""/>
    14851512</v:shape><![endif]--><![if !vml]><img border=0 width=747 height=600
    14861513src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image016.png"
    1487 v:shapes="Picture_x0020_27"><![endif]></span></p>
     1514v:shapes="_x0000_i1046"><![endif]></span></p>
    14881515
    14891516<p class=MsoNormal>It is obvious we have one very bad data point at a short
    … …  
    14941521"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:
    14951522minor-latin'>Index Peak List</span></b>. Select that data item from the tree.
    1496 The bad point is at the bottom of the table; uncheck the <b style='mso-bidi-font-weight:
    1497 normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
    1498 minor-latin;mso-hansi-theme-font:minor-latin'>use</span></b> box for it. Go
    1499 back to <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1500 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Instrument
    1501 Parameters</span></b> and repeat <b style='mso-bidi-font-weight:normal'><span
    1502 style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
    1503 mso-hansi-theme-font:minor-latin'>Operations/Calibrate</span></b>; the plot
    1504 will look a lot better.</p>
    1505 
    1506 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1507  id="Picture_x0020_28" o:spid="_x0000_i1029" type="#_x0000_t75" style='width:560.25pt;
    1508  height:450pt;visibility:visible;mso-wrap-style:square'>
     1523The bad point is at the bottom of the table; uncheck the <span class=SpellE><b
     1524style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1525mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>use</span></b></span>
     1526box for it. Go back to <b style='mso-bidi-font-weight:normal'><span
     1527style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1528mso-hansi-theme-font:minor-latin'>Instrument Parameters</span></b> and repeat <b
     1529style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1530mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Operations/Calibrate</span></b>;
     1531the plot will look a lot better.</p>
     1532
     1533<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1534 id="_x0000_i1045" type="#_x0000_t75" style='width:560.25pt;height:450pt;
     1535 visibility:visible;mso-wrap-style:square'>
    15091536 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image017.png"
    15101537  o:title=""/>
    15111538</v:shape><![endif]--><![if !vml]><img border=0 width=747 height=600
    15121539src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image017.png"
    1513 v:shapes="Picture_x0020_28"><![endif]></span></p>
     1540v:shapes="_x0000_i1045"><![endif]></span></p>
    15141541
    15151542<p class=MsoNormal>What is shown is the discrepancy between observed and
    1516 calculated position divided by the position vs d-spacing. The error bars
    1517 reflect the uncertainty in the fitted peak positions. The red dashed line is
    1518 obviously zero discrepancy and the blue dashed lines represent the width of a
    1519 data bin above and below zero (e.g. 2 bins from one blue line to the other) to
    1520 give you a sense of how significant the discrepancies are. One can improve the
    1521 fit by including the <b style='mso-bidi-font-weight:normal'><span
    1522 style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
    1523 mso-hansi-theme-font:minor-latin'>difB</span></b> parameter; select it and
    1524 repeat <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1525 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Operations/Calibrate</span></b>.
    1526 The fit is much improved.</p>
    1527 
    1528 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1529  id="Picture_x0020_29" o:spid="_x0000_i1028" type="#_x0000_t75" style='width:560.25pt;
     1543calculated position divided by the position (&#916;T/T) vs d-spacing. The error
     1544bars reflect the uncertainty in the fitted peak positions. The red dashed line
     1545is obviously zero discrepancy and the blue dashed lines represent the width of
     1546a data bin above and below zero (e.g. 2 bins from one blue line to the other)
     1547to give you a sense of how significant the discrepancies are. One can improve
     1548the fit by including the <span class=SpellE><b style='mso-bidi-font-weight:
     1549normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     1550minor-latin;mso-hansi-theme-font:minor-latin'>difA</span></b></span> parameter;
     1551select it and repeat <b style='mso-bidi-font-weight:normal'><span
     1552style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1553mso-hansi-theme-font:minor-latin'>Operations/Calibrate</span></b>. The fit is
     1554much improved.</p>
     1555
     1556<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1557 id="Picture_x0020_35" o:spid="_x0000_i1044" type="#_x0000_t75" style='width:525pt;
    15301558 height:450pt;visibility:visible;mso-wrap-style:square'>
    1531  <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image018.png"
    1532   o:title=""/>
    1533 </v:shape><![endif]--><![if !vml]><img border=0 width=747 height=600
    1534 src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image018.png"
    1535 v:shapes="Picture_x0020_29"><![endif]></span></p>
    1536 
    1537 <p class=MsoNormal>Notice that the deviation is largest at the larger
    1538 d-spacings; select <b style='mso-bidi-font-weight:normal'><span
    1539 style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
    1540 mso-hansi-theme-font:minor-latin'>difA</span></b> next and calibrate again. The
    1541 fit is better especially at the large d-spacings.</p>
    1542 
    1543 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1544  id="Picture_x0020_30" o:spid="_x0000_i1027" type="#_x0000_t75" style='width:560.25pt;
     1559 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image024.png"
     1560  o:title=""/>
     1561</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     1562src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image024.png"
     1563v:shapes="Picture_x0020_35"><![endif]></span></p>
     1564
     1565<p class=MsoNormal>One might get some improvement by refining Zero. I got the f<span
     1566style='mso-no-proof:yes'>ollowing new parameters<o:p></o:p></span></p>
     1567
     1568<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1569 id="Picture_x0020_36" o:spid="_x0000_i1043" type="#_x0000_t75" style='width:411pt;
     1570 height:203.25pt;visibility:visible;mso-wrap-style:square'>
     1571 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image025.png"
     1572  o:title=""/>
     1573</v:shape><![endif]--><![if !vml]><img border=0 width=548 height=271
     1574src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image025.png"
     1575v:shapes="Picture_x0020_36"><![endif]></span></p>
     1576
     1577<p class=MsoNormal>The fitted values are clearly within one half TOF bin of
     1578zero.</p>
     1579
     1580<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1581 id="Picture_x0020_33" o:spid="_x0000_i1042" type="#_x0000_t75" style='width:525pt;
    15451582 height:450pt;visibility:visible;mso-wrap-style:square'>
    1546  <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image019.png"
    1547   o:title=""/>
    1548 </v:shape><![endif]--><![if !vml]><img border=0 width=747 height=600
    1549 src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image019.png"
    1550 v:shapes="Picture_x0020_30"><![endif]></span></p>
    1551 
    1552 <p class=MsoNormal>Further improvement can be gained by including <b
    1553 style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    1554 mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Zero</span></b>.
    1555 The result is</p>
    1556 
    1557 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1558  id="Picture_x0020_31" o:spid="_x0000_i1026" type="#_x0000_t75" style='width:560.25pt;
    1559  height:450pt;visibility:visible;mso-wrap-style:square'>
    1560  <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image020.png"
    1561   o:title=""/>
    1562 </v:shape><![endif]--><![if !vml]><img border=0 width=747 height=600
    1563 src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image020.png"
    1564 v:shapes="Picture_x0020_31"><![endif]></span></p>
    1565 
    1566 <p class=MsoNormal>with the new parameters</p>
    1567 
    1568 <p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
    1569  id="Picture_x0020_32" o:spid="_x0000_i1025" type="#_x0000_t75" style='width:411pt;
    1570  height:203.25pt;visibility:visible;mso-wrap-style:square'>
    1571  <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image021.png"
    1572   o:title=""/>
    1573 </v:shape><![endif]--><![if !vml]><img border=0 width=548 height=271
    1574 src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image021.png"
    1575 v:shapes="Picture_x0020_32"><![endif]></span></p>
    1576 
    1577 <p class=MsoNormal>These new instrument parameters can be saved for later use;
     1583 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image026.png"
     1584  o:title=""/>
     1585</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     1586src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image026.png"
     1587v:shapes="Picture_x0020_33"><![endif]></span></p>
     1588
     1589<p class=MsoNormal>As these values have now been established, uncheck all their
     1590refinement boxes. These new instrument parameters can be saved for later use;
    15781591select <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    15791592mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Operations/Save
    … …  
    15811594</span></b> from the menu. A file name is requested (no extension);
    15821595this file can be used in place of the old GSAS instrument parameter file when
    1583 reading new data for this instrument. Notice that we did not establish values
    1584 for the instrument profile coefficients (alpha, beta &amp; sig terms). These
    1585 are best set <i style='mso-bidi-font-style:normal'>via</i> Rietveld refinement
    1586 of a suitable standard (SRM 660b La<sup>10</sup>B<sub>6</sub> is good for
    1587 this). This ends this tutorial exercise; you may save the project if you wish,
     1596reading new data for this instrument. This ends the first part of this tutorial
     1597exercise; you may save the project if you wish, select <b style='mso-bidi-font-weight:
     1598normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     1599minor-latin;mso-hansi-theme-font:minor-latin'>File/Save project</span></b> from
     1600the GSAS-II data tree window. Notice that we did not establish values for the
     1601instrument profile coefficients (alpha, beta &amp; sig terms). These will be
     1602established in the second part of the tutorial.</p>
     1603
     1604<h1>Part II. Determine the instrument profile coefficients</h1>
     1605
     1606<p class=MsoNormal>To best establish the profile coefficients one must have the
     1607best model for the fitting. In this case we will change the background function
     1608to something more flexible than the 6 term <span class=SpellE>chebyschev</span>
     1609function used above and add all visible peaks beyond those found by the
     1610automatic procedure used above.</p>
     1611
     1612<h2>Step 1. Change background</h2>
     1613
     1614<p class=MsoNormal>Select the <b style='mso-bidi-font-weight:normal'><span
     1615style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1616mso-hansi-theme-font:minor-latin'>Background</span></b> tree item; you should
     1617see</p>
     1618
     1619<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1620 id="Picture_x0020_18" o:spid="_x0000_i1041" type="#_x0000_t75" style='width:402pt;
     1621 height:160.5pt;visibility:visible;mso-wrap-style:square'>
     1622 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image027.png"
     1623  o:title=""/>
     1624</v:shape><![endif]--><![if !vml]><img border=0 width=536 height=214
     1625src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image027.png"
     1626v:shapes="Picture_x0020_18"><![endif]></span></p>
     1627
     1628<p class=MsoNormal>From the <b style='mso-bidi-font-weight:normal'><span
     1629style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1630mso-hansi-theme-font:minor-latin'>Background function</span></b> pulldown,
    15881631select <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1632mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>log
     1633interpolate</span></b> and set the <b style='mso-bidi-font-weight:normal'><span
     1634style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1635mso-hansi-theme-font:minor-latin'>No. <span class=SpellE>coeff</span>.</span></b>
     1636<span class=GramE>to</span> <b style='mso-bidi-font-weight:normal'><span
     1637style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1638mso-hansi-theme-font:minor-latin'>10</span></b>. This will select 10 fixed
     1639position points across the pattern between the limits located in constant <span
     1640class=GramE>log(</span>TOF) steps; this puts more points at the short TOF end
     1641of the pattern where the background is changing most rapidly. Return to <b
     1642style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1643mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Peak List</span></b>
     1644and do <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1645mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Peak
     1646Fitting/<span class=SpellE>Peakfit</span></span></b>; this should give a better
     1647fit to the background.</p>
     1648
     1649<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1650 id="Picture_x0020_19" o:spid="_x0000_i1040" type="#_x0000_t75" style='width:525pt;
     1651 height:450pt;visibility:visible;mso-wrap-style:square'>
     1652 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image028.png"
     1653  o:title=""/>
     1654</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     1655src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image028.png"
     1656v:shapes="Picture_x0020_19"><![endif]></span></p>
     1657
     1658<h2>Step 2. Add more peaks to be fitted</h2>
     1659
     1660<p class=MsoNormal>Now zoom in on the right hand end of the pattern and select
     1661every unmarked peak you can see. Be sure the zoom button is off and you can use
     1662the &lt; &gt; buttons to shift the pattern left or right. It is essential to
     1663include as many peaks as possible because including them forces the background
     1664to its “true” level and thus giving each peak its true shape. The high Q end of
     1665my pattern looked like</p>
     1666
     1667<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1668 id="Picture_x0020_20" o:spid="_x0000_i1039" type="#_x0000_t75" style='width:525pt;
     1669 height:450pt;visibility:visible;mso-wrap-style:square'>
     1670 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image029.png"
     1671  o:title=""/>
     1672</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     1673src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image029.png"
     1674v:shapes="Picture_x0020_20"><![endif]></span></p>
     1675
     1676<p class=MsoNormal>When I was done; I had 128 peaks. Do <b style='mso-bidi-font-weight:
     1677normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     1678minor-latin;mso-hansi-theme-font:minor-latin'>Peak fitting/<span class=SpellE>Peakfit</span></span></b>;
     1679all peaks should fit in a few seconds and the background line should drop a bit.</p>
     1680
     1681<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1682 id="Picture_x0020_21" o:spid="_x0000_i1038" type="#_x0000_t75" style='width:525pt;
     1683 height:450pt;visibility:visible;mso-wrap-style:square'>
     1684 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image030.png"
     1685  o:title=""/>
     1686</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     1687src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image030.png"
     1688v:shapes="Picture_x0020_21"><![endif]></span></p>
     1689
     1690<p class=MsoNormal>I’ve dragged the difference curve up so you can see it.
     1691Notice that it is mostly from position errors; so set the refine boxes for
     1692position (<span class=SpellE>i.e</span> pick a box, pick the <b
     1693style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1694mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>refine</span></b>
     1695column heading &amp; press <b style='mso-bidi-font-weight:normal'><span
     1696style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1697mso-hansi-theme-font:minor-latin'>y</span></b>). Repeat <b style='mso-bidi-font-weight:
     1698normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     1699minor-latin;mso-hansi-theme-font:minor-latin'>Peak Fitting/<span class=SpellE>Peakfit</span></span></b>;
     1700the fit will improve. On the console listing before the peak listing the
     1701residuals are shown; <span class=SpellE>Rwp</span> ~10.0%</p>
     1702
     1703<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1704 id="Picture_x0020_22" o:spid="_x0000_i1037" type="#_x0000_t75" style='width:525pt;
     1705 height:450pt;visibility:visible;mso-wrap-style:square'>
     1706 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image031.png"
     1707  o:title=""/>
     1708</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     1709src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image031.png"
     1710v:shapes="Picture_x0020_22"><![endif]></span></p>
     1711
     1712<p class=MsoNormal>You might want to save the project at this point; do <b
     1713style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
    15891714mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>File/Save
    1590 project</span></b> from the GSAS-II data tree window.</p>
     1715project</span></b> from the main GSAS-II data tree window.</p>
     1716
     1717<h2>Step 3. Refine profile coefficients</h2>
     1718
     1719<p class=MsoNormal>In this step you will be selecting some profile coefficients
     1720(alpha to sig-q) for refinement, doing peak fits and hopefully improving the
     1721fit to the profile. Occasionally the refinement will diverge or fail; use the <b
     1722style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1723mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Peak
     1724fitting/Undo</span></b> command immediately to recover. The Background,
     1725Instrument Parameters and Peak List values will all be restored. Select <b
     1726style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1727mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Instrument
     1728Parameters</span></b> from the GSAS-II data tree; the data window will show</p>
     1729
     1730<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1731 id="Picture_x0020_37" o:spid="_x0000_i1036" type="#_x0000_t75" style='width:411pt;
     1732 height:203.25pt;visibility:visible;mso-wrap-style:square'>
     1733 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image032.png"
     1734  o:title=""/>
     1735</v:shape><![endif]--><![if !vml]><img border=0 width=548 height=271
     1736src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image032.png"
     1737v:shapes="Picture_x0020_37"><![endif]></span></p>
     1738
     1739<p class=MsoNormal>You should realize that alpha largely affects the sharpness
     1740of the leading TOF edge of each peak; larger values mean sharper front edges.
     1741Beta terms affect the trailing TOF edge in the same way. Sig terms affect the
     1742Gaussian shape component of the peak profiles; larger values result in broader
     1743peaks. The coefficients describe the alpha, beta and sig values as follows:</p>
     1744
     1745<p class=MsoNormal><!--[if gte msEquation 12]><m:oMath><i style='mso-bidi-font-style:
     1746 normal'><span style='font-family:"Cambria Math",serif'><m:r>&#945;</m:r><m:r>=</m:r></span></i><m:f><m:fPr><m:type
     1747    m:val="skw"/><span style='font-family:"Cambria Math",serif;mso-ascii-font-family:
     1748   "Cambria Math";mso-hansi-font-family:"Cambria Math";font-style:italic;
     1749   mso-bidi-font-style:normal'><m:ctrlPr></m:ctrlPr></span></m:fPr><m:num><m:sSub><m:sSubPr><span
     1750     style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1751     mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1752     normal'><m:ctrlPr></m:ctrlPr></span></m:sSubPr><m:e><i style='mso-bidi-font-style:
     1753     normal'><span style='font-family:"Cambria Math",serif'><m:r>&#945;</m:r></span></i></m:e><m:sub><i
     1754     style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>0</m:r></span></i></m:sub></m:sSub></m:num><m:den><i
     1755   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>d</m:r></span></i></m:den></m:f></m:oMath><![endif]--><![if !msEquation]><span
     1756style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1757"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1758top:6.0pt;mso-text-raise:-6.0pt;mso-ansi-language:EN-US;mso-fareast-language:
     1759EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1760 type="#_x0000_t75" style='width:48pt;height:19.5pt'>
     1761 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image033.png"
     1762  o:title="" chromakey="white"/>
     1763</v:shape><![endif]--><![if !vml]><img width=64 height=26
     1764src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image019.png"
     1765v:shapes="_x0000_i1025"><![endif]></span><![endif]><span
     1766style='mso-spacerun:yes'>    </span><span style='mso-spacerun:yes'> </span><!--[if gte msEquation 12]><m:oMath><i
     1767 style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>&#946;</m:r><m:r>=</m:r></span></i><m:sSub><m:sSubPr><span
     1768   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1769   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1770   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubPr><m:e><i style='mso-bidi-font-style:
     1771   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#946;</m:r></span></i></m:e><m:sub><i
     1772   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>0</m:r></span></i></m:sub></m:sSub><i
     1773 style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>+</m:r></span></i><m:f><m:fPr><m:type
     1774    m:val="skw"/><span style='font-family:"Cambria Math",serif;mso-ascii-font-family:
     1775   "Cambria Math";mso-hansi-font-family:"Cambria Math";font-style:italic;
     1776   mso-bidi-font-style:normal'><m:ctrlPr></m:ctrlPr></span></m:fPr><m:num><m:sSub><m:sSubPr><span
     1777     style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1778     mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1779     normal'><m:ctrlPr></m:ctrlPr></span></m:sSubPr><m:e><i style='mso-bidi-font-style:
     1780     normal'><span style='font-family:"Cambria Math",serif'><m:r>&#946;</m:r></span></i></m:e><m:sub><i
     1781     style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>1</m:r></span></i></m:sub></m:sSub></m:num><m:den><m:sSup><m:sSupPr><span
     1782     style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1783     mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1784     normal'><m:ctrlPr></m:ctrlPr></span></m:sSupPr><m:e><i style='mso-bidi-font-style:
     1785     normal'><span style='font-family:"Cambria Math",serif'><m:r>d</m:r></span></i></m:e><m:sup><i
     1786     style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>4</m:r></span></i></m:sup></m:sSup></m:den></m:f><i
     1787 style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>+</m:r></span></i><m:f><m:fPr><m:type
     1788    m:val="skw"/><span style='font-family:"Cambria Math",serif;mso-ascii-font-family:
     1789   "Cambria Math";mso-hansi-font-family:"Cambria Math";font-style:italic;
     1790   mso-bidi-font-style:normal'><m:ctrlPr></m:ctrlPr></span></m:fPr><m:num><m:sSub><m:sSubPr><span
     1791     style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1792     mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1793     normal'><m:ctrlPr></m:ctrlPr></span></m:sSubPr><m:e><i style='mso-bidi-font-style:
     1794     normal'><span style='font-family:"Cambria Math",serif'><m:r>&#946;</m:r></span></i></m:e><m:sub><i
     1795     style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>q</m:r></span></i></m:sub></m:sSub></m:num><m:den><m:sSup><m:sSupPr><span
     1796     style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1797     mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1798     normal'><m:ctrlPr></m:ctrlPr></span></m:sSupPr><m:e><i style='mso-bidi-font-style:
     1799     normal'><span style='font-family:"Cambria Math",serif'><m:r>d</m:r></span></i></m:e><m:sup><i
     1800     style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSup></m:den></m:f></m:oMath><![endif]--><![if !msEquation]><span
     1801style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1802"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1803top:7.0pt;mso-text-raise:-7.0pt;mso-ansi-language:EN-US;mso-fareast-language:
     1804EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1805 type="#_x0000_t75" style='width:123pt;height:24pt'>
     1806 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image035.png"
     1807  o:title="" chromakey="white"/>
     1808</v:shape><![endif]--><![if !vml]><img width=164 height=32
     1809src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image020.png"
     1810v:shapes="_x0000_i1025"><![endif]></span><![endif]><span
     1811style='mso-spacerun:yes'> </span><!--[if gte msEquation 12]><m:oMath><m:sSup><m:sSupPr><span
     1812   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1813   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1814   normal'><m:ctrlPr></m:ctrlPr></span></m:sSupPr><m:e><i style='mso-bidi-font-style:
     1815   normal'><span style='font-family:"Cambria Math",serif'><m:r><span
     1816    style='mso-spacerun:yes'>      </span></m:r><m:r>&#963;</m:r></span></i></m:e><m:sup><i
     1817   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSup><i
     1818 style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>=</m:r></span></i><m:sSubSup><m:sSubSupPr><span
     1819   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1820   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1821   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubSupPr><m:e><i style='mso-bidi-font-style:
     1822   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#963;</m:r></span></i></m:e><m:sub><i
     1823   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>0</m:r></span></i></m:sub><m:sup><i
     1824   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSubSup><i
     1825 style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>+</m:r></span></i><m:sSubSup><m:sSubSupPr><span
     1826   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1827   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1828   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubSupPr><m:e><i style='mso-bidi-font-style:
     1829   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#963;</m:r></span></i></m:e><m:sub><i
     1830   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>1</m:r></span></i></m:sub><m:sup><i
     1831   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSubSup><m:sSup><m:sSupPr><span
     1832   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1833   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1834   normal'><m:ctrlPr></m:ctrlPr></span></m:sSupPr><m:e><i style='mso-bidi-font-style:
     1835   normal'><span style='font-family:"Cambria Math",serif'><m:r>d</m:r></span></i></m:e><m:sup><i
     1836   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSup><i
     1837 style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>+</m:r></span></i><m:sSubSup><m:sSubSupPr><span
     1838   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1839   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1840   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubSupPr><m:e><i style='mso-bidi-font-style:
     1841   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#963;</m:r></span></i></m:e><m:sub><i
     1842   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sub><m:sup><i
     1843   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSubSup><m:sSup><m:sSupPr><span
     1844   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1845   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1846   normal'><m:ctrlPr></m:ctrlPr></span></m:sSupPr><m:e><i style='mso-bidi-font-style:
     1847   normal'><span style='font-family:"Cambria Math",serif'><m:r>d</m:r></span></i></m:e><m:sup><i
     1848   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>4</m:r></span></i></m:sup></m:sSup><i
     1849 style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>+</m:r></span></i><m:f><m:fPr><m:type
     1850    m:val="skw"/><span style='font-family:"Cambria Math",serif;mso-ascii-font-family:
     1851   "Cambria Math";mso-hansi-font-family:"Cambria Math";font-style:italic;
     1852   mso-bidi-font-style:normal'><m:ctrlPr></m:ctrlPr></span></m:fPr><m:num><m:sSubSup><m:sSubSupPr><span
     1853     style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1854     mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1855     normal'><m:ctrlPr></m:ctrlPr></span></m:sSubSupPr><m:e><i
     1856     style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>&#963;</m:r></span></i></m:e><m:sub><i
     1857     style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>q</m:r></span></i></m:sub><m:sup><i
     1858     style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSubSup></m:num><m:den><m:sSup><m:sSupPr><span
     1859     style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1860     mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1861     normal'><m:ctrlPr></m:ctrlPr></span></m:sSupPr><m:e><i style='mso-bidi-font-style:
     1862     normal'><span style='font-family:"Cambria Math",serif'><m:r>d</m:r></span></i></m:e><m:sup><i
     1863     style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSup></m:den></m:f></m:oMath><![endif]--><![if !msEquation]><span
     1864style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1865"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1866top:7.0pt;mso-text-raise:-7.0pt;mso-ansi-language:EN-US;mso-fareast-language:
     1867EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1868 type="#_x0000_t75" style='width:183pt;height:25.5pt'>
     1869 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image037.png"
     1870  o:title="" chromakey="white"/>
     1871</v:shape><![endif]--><![if !vml]><img width=244 height=34
     1872src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image021.png"
     1873v:shapes="_x0000_i1025"><![endif]></span><![endif]></p>
     1874
     1875<p class=MsoNormal><o:p>&nbsp;</o:p></p>
     1876
     1877<p class=MsoNormal>The refinable coefficients are: alpha (&#945;<sub>0</sub>), beta-0
     1878(<!--[if gte msEquation 12]><m:oMath><m:sSub><m:sSubPr><span style='font-family:
     1879   "Cambria Math",serif;mso-ascii-font-family:"Cambria Math";mso-hansi-font-family:
     1880   "Cambria Math";font-style:italic;mso-bidi-font-style:normal'><m:ctrlPr></m:ctrlPr></span></m:sSubPr><m:e><i
     1881   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>&#946;</m:r></span></i></m:e><m:sub><i
     1882   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>0</m:r></span></i></m:sub></m:sSub></m:oMath><![endif]--><![if !msEquation]><span
     1883style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1884"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1885top:3.0pt;mso-text-raise:-3.0pt;mso-ansi-language:EN-US;mso-fareast-language:
     1886EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1887 type="#_x0000_t75" style='width:12pt;height:14.25pt'>
     1888 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image039.png"
     1889  o:title="" chromakey="white"/>
     1890</v:shape><![endif]--><![if !vml]><img width=16 height=19
     1891src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image064.png"
     1892v:shapes="_x0000_i1025"><![endif]></span><![endif]>), beta-1 (<!--[if gte msEquation 12]><m:oMath><m:sSub><m:sSubPr><span
     1893   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1894   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1895   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubPr><m:e><i style='mso-bidi-font-style:
     1896   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#946;</m:r></span></i></m:e><m:sub><i
     1897   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>1</m:r></span></i></m:sub></m:sSub></m:oMath><![endif]--><![if !msEquation]><span
     1898style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1899"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1900top:3.0pt;mso-text-raise:-3.0pt;mso-ansi-language:EN-US;mso-fareast-language:
     1901EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1902 type="#_x0000_t75" style='width:12pt;height:14.25pt'>
     1903 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image041.png"
     1904  o:title="" chromakey="white"/>
     1905</v:shape><![endif]--><![if !vml]><img width=16 height=19
     1906src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image065.png"
     1907v:shapes="_x0000_i1025"><![endif]></span><![endif]>), beta-q (<!--[if gte msEquation 12]><m:oMath><m:sSub><m:sSubPr><span
     1908   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1909   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1910   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubPr><m:e><i style='mso-bidi-font-style:
     1911   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#946;</m:r></span></i></m:e><m:sub><i
     1912   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>q</m:r></span></i></m:sub></m:sSub></m:oMath><![endif]--><![if !msEquation]><span
     1913style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1914"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1915top:4.5pt;mso-text-raise:-4.5pt;mso-ansi-language:EN-US;mso-fareast-language:
     1916EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1917 type="#_x0000_t75" style='width:12pt;height:15.75pt'>
     1918 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image043.png"
     1919  o:title="" chromakey="white"/>
     1920</v:shape><![endif]--><![if !vml]><img width=16 height=21
     1921src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image066.png"
     1922v:shapes="_x0000_i1025"><![endif]></span><![endif]>), sig-0 (<!--[if gte msEquation 12]><m:oMath><m:sSubSup><m:sSubSupPr><span
     1923   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1924   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1925   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubSupPr><m:e><i style='mso-bidi-font-style:
     1926   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#963;</m:r></span></i></m:e><m:sub><i
     1927   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>0</m:r></span></i></m:sub><m:sup><i
     1928   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSubSup></m:oMath><![endif]--><![if !msEquation]><span
     1929style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1930"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1931top:3.0pt;mso-text-raise:-3.0pt;mso-ansi-language:EN-US;mso-fareast-language:
     1932EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1933 type="#_x0000_t75" style='width:13.5pt;height:14.25pt'>
     1934 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image045.png"
     1935  o:title="" chromakey="white"/>
     1936</v:shape><![endif]--><![if !vml]><img width=18 height=19
     1937src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image067.png"
     1938v:shapes="_x0000_i1025"><![endif]></span><![endif]>), sig-1 (<!--[if gte msEquation 12]><m:oMath><m:sSubSup><m:sSubSupPr><span
     1939   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1940   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1941   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubSupPr><m:e><i style='mso-bidi-font-style:
     1942   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#963;</m:r></span></i></m:e><m:sub><i
     1943   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>1</m:r></span></i></m:sub><m:sup><i
     1944   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSubSup></m:oMath><![endif]--><![if !msEquation]><span
     1945style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1946"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1947top:3.0pt;mso-text-raise:-3.0pt;mso-ansi-language:EN-US;mso-fareast-language:
     1948EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1949 type="#_x0000_t75" style='width:13.5pt;height:14.25pt'>
     1950 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image047.png"
     1951  o:title="" chromakey="white"/>
     1952</v:shape><![endif]--><![if !vml]><img width=18 height=19
     1953src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image068.png"
     1954v:shapes="_x0000_i1025"><![endif]></span><![endif]>), sig-2 (<!--[if gte msEquation 12]><m:oMath><m:sSubSup><m:sSubSupPr><span
     1955   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1956   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1957   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubSupPr><m:e><i style='mso-bidi-font-style:
     1958   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#963;</m:r></span></i></m:e><m:sub><i
     1959   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sub><m:sup><i
     1960   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSubSup></m:oMath><![endif]--><![if !msEquation]><span
     1961style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1962"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1963top:3.0pt;mso-text-raise:-3.0pt;mso-ansi-language:EN-US;mso-fareast-language:
     1964EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1965 type="#_x0000_t75" style='width:13.5pt;height:14.25pt'>
     1966 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image049.png"
     1967  o:title="" chromakey="white"/>
     1968</v:shape><![endif]--><![if !vml]><img width=18 height=19
     1969src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image069.png"
     1970v:shapes="_x0000_i1025"><![endif]></span><![endif]>) and sig-q (<!--[if gte msEquation 12]><m:oMath><m:sSubSup><m:sSubSupPr><span
     1971   style='font-family:"Cambria Math",serif;mso-ascii-font-family:"Cambria Math";
     1972   mso-hansi-font-family:"Cambria Math";font-style:italic;mso-bidi-font-style:
     1973   normal'><m:ctrlPr></m:ctrlPr></span></m:sSubSupPr><m:e><i style='mso-bidi-font-style:
     1974   normal'><span style='font-family:"Cambria Math",serif'><m:r>&#963;</m:r></span></i></m:e><m:sub><i
     1975   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>q</m:r></span></i></m:sub><m:sup><i
     1976   style='mso-bidi-font-style:normal'><span style='font-family:"Cambria Math",serif'><m:r>2</m:r></span></i></m:sup></m:sSubSup></m:oMath><![endif]--><![if !msEquation]><span
     1977style='font-size:12.0pt;font-family:"Times New Roman",serif;mso-fareast-font-family:
     1978"Times New Roman";mso-fareast-theme-font:minor-fareast;position:relative;
     1979top:4.5pt;mso-text-raise:-4.5pt;mso-ansi-language:EN-US;mso-fareast-language:
     1980EN-US;mso-bidi-language:AR-SA'><!--[if gte vml 1]><v:shape id="_x0000_i1025"
     1981 type="#_x0000_t75" style='width:13.5pt;height:15.75pt'>
     1982 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image051.png"
     1983  o:title="" chromakey="white"/>
     1984</v:shape><![endif]--><![if !vml]><img width=18 height=21
     1985src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image070.png"
     1986v:shapes="_x0000_i1025"><![endif]></span><![endif]>). Some of the values given
     1987above are probably not appropriate; looking at the difference curve it appears
     1988that the peak width is most in error. Refine <b style='mso-bidi-font-weight:
     1989normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     1990minor-latin;mso-hansi-theme-font:minor-latin'>sig-1</span></b> and <b
     1991style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     1992mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>sig-2</span></b>.
     1993Remember to go back to <b style='mso-bidi-font-weight:normal'><span
     1994style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     1995mso-hansi-theme-font:minor-latin'>Peak List</span></b> to do the fitting. My <span
     1996class=SpellE>Rwp</span> improved to 7.32% and the new coefficients looked like</p>
     1997
     1998<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     1999 id="Picture_x0020_38" o:spid="_x0000_i1035" type="#_x0000_t75" style='width:411pt;
     2000 height:220.5pt;visibility:visible;mso-wrap-style:square'>
     2001 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image053.png"
     2002  o:title=""/>
     2003</v:shape><![endif]--><![if !vml]><img border=0 width=548 height=294
     2004src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image053.png"
     2005v:shapes="Picture_x0020_38"><![endif]></span></p>
     2006
     2007<p class=MsoNormal>After adding <b style='mso-bidi-font-weight:normal'><span
     2008style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     2009mso-hansi-theme-font:minor-latin'>sig-0</span></b> and <b style='mso-bidi-font-weight:
     2010normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     2011minor-latin;mso-hansi-theme-font:minor-latin'>sig-q</span></b> to the refinement,
     2012my residual improved slightly to <span class=SpellE>Rwp</span>=6.9%. A zoom
     2013view of some peaks around TOF~20000µs</p>
     2014
     2015<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2016 id="Picture_x0020_25" o:spid="_x0000_i1034" type="#_x0000_t75" style='width:525pt;
     2017 height:450pt;visibility:visible;mso-wrap-style:square'>
     2018 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image054.png"
     2019  o:title=""/>
     2020</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     2021src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image054.png"
     2022v:shapes="Picture_x0020_25"><![endif]></span></p>
     2023
     2024<p class=MsoNormal>Suggests that the beta terms are too large, i.e. the
     2025trailing edges are calculating too sharp compared to the data. In two steps
     2026first add <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     2027mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>beta-0</span></b>
     2028to the refinement and then second add <b style='mso-bidi-font-weight:normal'><span
     2029style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     2030mso-hansi-theme-font:minor-latin'>beta-1</span></b>. The two refinements improve
     2031the fit (<span class=SpellE>Rwp</span>=6.23% after the 1<sup>st</sup> step and <span
     2032class=SpellE>Rwp</span>=5.50% after the 2<sup>nd</sup>). The resulting coefficients
     2033are</p>
     2034
     2035<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2036 id="Picture_x0020_39" o:spid="_x0000_i1033" type="#_x0000_t75" style='width:411pt;
     2037 height:220.5pt;visibility:visible;mso-wrap-style:square'>
     2038 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image055.png"
     2039  o:title=""/>
     2040</v:shape><![endif]--><![if !vml]><img border=0 width=548 height=294
     2041src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image055.png"
     2042v:shapes="Picture_x0020_39"><![endif]></span></p>
     2043
     2044<p class=MsoNormal>And the fit in the above region is now much better.</p>
     2045
     2046<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2047 id="Picture_x0020_27" o:spid="_x0000_i1032" type="#_x0000_t75" style='width:525pt;
     2048 height:450pt;visibility:visible;mso-wrap-style:square'>
     2049 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image056.png"
     2050  o:title=""/>
     2051</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     2052src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image056.png"
     2053v:shapes="Picture_x0020_27"><![endif]></span></p>
     2054
     2055<p class=MsoNormal>The principal errors now seem to be on the front edge of the
     2056peaks. After adding <b style='mso-bidi-font-weight:normal'><span
     2057style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     2058mso-hansi-theme-font:minor-latin'>alpha</span></b> to the refinement, I got <span
     2059class=SpellE>Rwp</span>=4.35% and the difference curve is almost flat.</p>
     2060
     2061<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2062 id="Picture_x0020_28" o:spid="_x0000_i1031" type="#_x0000_t75" style='width:525pt;
     2063 height:450pt;visibility:visible;mso-wrap-style:square'>
     2064 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image057.png"
     2065  o:title=""/>
     2066</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     2067src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image057.png"
     2068v:shapes="Picture_x0020_28"><![endif]></span></p>
     2069
     2070<p class=MsoNormal>The coefficients are</p>
     2071
     2072<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2073 id="Picture_x0020_40" o:spid="_x0000_i1030" type="#_x0000_t75" style='width:411pt;
     2074 height:220.5pt;visibility:visible;mso-wrap-style:square'>
     2075 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image058.png"
     2076  o:title=""/>
     2077</v:shape><![endif]--><![if !vml]><img border=0 width=548 height=294
     2078src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image058.png"
     2079v:shapes="Picture_x0020_40"><![endif]></span></p>
     2080
     2081<p class=MsoNormal>As this represents a very good fit to the profile, it would
     2082be useful to save the project (do <b style='mso-bidi-font-weight:normal'><span
     2083style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     2084mso-hansi-theme-font:minor-latin'>File/Save project</span></b> from the main
     2085GSAS-II data tree menu) and make a new instrument file (do <b style='mso-bidi-font-weight:
     2086normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     2087minor-latin;mso-hansi-theme-font:minor-latin'>Operations/Save profile</span></b>
     2088from the Instrument Parameters menu; you can overwrite the existing one). I did
     2089try to refine beta-q; that gave a failed refinement. However, the material used
     2090for the calibration (SRM 660b La10B6) does have some sample broadening. As this
     2091almost always shows up as a Lorentzian contribution to the peak profiles one
     2092can accommodate it by refining <b style='mso-bidi-font-weight:normal'><span
     2093style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     2094mso-hansi-theme-font:minor-latin'>X</span></b> and <b style='mso-bidi-font-weight:
     2095normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     2096minor-latin;mso-hansi-theme-font:minor-latin'>Y</span></b>. After refining them
     2097I get a substantial improvement <span class=SpellE>Rwp</span>=3.24% and there
     2098are considerable changes in the other coefficients because they no longer have
     2099to compensate for the missing Lorentzian component. Their values then represent
     2100the instrument contribution to the profile.</p>
     2101
     2102<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2103 id="Picture_x0020_41" o:spid="_x0000_i1029" type="#_x0000_t75" style='width:411pt;
     2104 height:220.5pt;visibility:visible;mso-wrap-style:square'>
     2105 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image059.png"
     2106  o:title=""/>
     2107</v:shape><![endif]--><![if !vml]><img border=0 width=548 height=294
     2108src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image059.png"
     2109v:shapes="Picture_x0020_41"><![endif]></span></p>
     2110
     2111<p class=MsoNormal>The profile fit is almost perfect</p>
     2112
     2113<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2114 id="Picture_x0020_31" o:spid="_x0000_i1028" type="#_x0000_t75" style='width:525pt;
     2115 height:450pt;visibility:visible;mso-wrap-style:square'>
     2116 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image060.png"
     2117  o:title=""/>
     2118</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     2119src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image060.png"
     2120v:shapes="Picture_x0020_31"><![endif]></span></p>
     2121
     2122<p class=MsoNormal>I’ve switched back to a q plot and positioned the difference
     2123curve to be about zero.</p>
     2124
     2125<h2>Step 4. Check diffractometer constants </h2>
     2126
     2127<p class=MsoNormal>Since these calibration fits for profile coefficients varied
     2128the peak positions, a final check on the diffractometer constants is needed. To
     2129do this, the new peak positions need to be loaded into the <b style='mso-bidi-font-weight:
     2130normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     2131minor-latin;mso-hansi-theme-font:minor-latin'>Index Peak List</span></b> (do <b
     2132style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     2133mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Operations/Load/Reload</span></b>
     2134in that menu). Notice that the Index peaks are no longer indexed. In <b
     2135style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     2136mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Unit Cells
     2137List</span></b>, press the <b style='mso-bidi-font-weight:normal'><span
     2138style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     2139mso-hansi-theme-font:minor-latin'>Show <span class=SpellE>hkl</span> positions</span></b>
     2140button; this will index the lines. The go to <b style='mso-bidi-font-weight:
     2141normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     2142minor-latin;mso-hansi-theme-font:minor-latin'>Instrument Parameters</span></b>
     2143and uncheck all the profile coefficient <b style='mso-bidi-font-weight:normal'><span
     2144style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     2145mso-hansi-theme-font:minor-latin'>Refine?</span></b> <span class=GramE>boxes</span>;
     2146then check those you varied at the beginning of the tutorial (<span
     2147class=SpellE><b style='mso-bidi-font-weight:normal'><span style='font-family:
     2148"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:
     2149minor-latin'>difC</span></b></span>, <span class=SpellE><b style='mso-bidi-font-weight:
     2150normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     2151minor-latin;mso-hansi-theme-font:minor-latin'>difA</span></b></span> &amp; <b
     2152style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     2153mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Zero</span></b>).
     2154Do <b style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     2155mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>Operations/Calibrate</span></b>.
     2156The agreement shows some deviations at very short d-spacing that weren’t
     2157evident in the initial calibration.</p>
     2158
     2159<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2160 id="Picture_x0020_42" o:spid="_x0000_i1027" type="#_x0000_t75" style='width:525pt;
     2161 height:450pt;visibility:visible;mso-wrap-style:square'>
     2162 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image061.png"
     2163  o:title=""/>
     2164</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     2165src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image061.png"
     2166v:shapes="Picture_x0020_42"><![endif]></span></p>
     2167
     2168<p class=MsoNormal>You will need to add the <span class=SpellE><b
     2169style='mso-bidi-font-weight:normal'><span style='font-family:"Calibri",sans-serif;
     2170mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:minor-latin'>difB</span></b></span>
     2171parameter to the fit. Check the box and repeat <b style='mso-bidi-font-weight:
     2172normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     2173minor-latin;mso-hansi-theme-font:minor-latin'>Operations/Calibrate</span></b>.
     2174The fit now is better apart from a few stragglers at low d-<span class=SpellE>spacings</span></p>
     2175
     2176<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2177 id="Picture_x0020_43" o:spid="_x0000_i1026" type="#_x0000_t75" style='width:525pt;
     2178 height:450pt;visibility:visible;mso-wrap-style:square'>
     2179 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image062.png"
     2180  o:title=""/>
     2181</v:shape><![endif]--><![if !vml]><img border=0 width=700 height=600
     2182src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image062.png"
     2183v:shapes="Picture_x0020_43"><![endif]></span></p>
     2184
     2185<p class=MsoNormal>These are very weak peaks whose position was poorly
     2186determined. Almost all the rest are within a 1TOF bin width around zero. Save
     2187the project <b style='mso-bidi-font-weight:normal'><span style='font-family:
     2188"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:
     2189minor-latin'>(File/Save project</span></b> in the main GSAS-II data tree menu).</p>
     2190
     2191<h2>Step 5. Make instrument parameter file</h2>
     2192
     2193<p class=MsoNormal>We now have a fully calibrated instrument with
     2194diffractometer coefficients and profile coefficients. Uncheck all refinement
     2195boxes and set <b style='mso-bidi-font-weight:normal'><span style='font-family:
     2196"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;mso-hansi-theme-font:
     2197minor-latin'>X</span></b> and <b style='mso-bidi-font-weight:normal'><span
     2198style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     2199mso-hansi-theme-font:minor-latin'>Y</span></b> back to zero. You should have</p>
     2200
     2201<p class=MsoNormal><span style='mso-no-proof:yes'><!--[if gte vml 1]><v:shape
     2202 id="Picture_x0020_45" o:spid="_x0000_i1025" type="#_x0000_t75" style='width:411pt;
     2203 height:203.25pt;visibility:visible;mso-wrap-style:square'>
     2204 <v:imagedata src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image063.png"
     2205  o:title=""/>
     2206</v:shape><![endif]--><![if !vml]><img border=0 width=548 height=271
     2207src="Calibration%20of%20a%20TOF%20powder%20diffractometer_files/image063.png"
     2208v:shapes="Picture_x0020_45"><![endif]></span></p>
     2209
     2210<p class=MsoNormal>This removes from the instrument parameters any sample broadening
     2211effects and thus the remaining parameters are only dependent on the instrument.
     2212To make an instrument parameter file do <b style='mso-bidi-font-weight:normal'><span
     2213style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
     2214mso-hansi-theme-font:minor-latin'>Operations/Save profile</span></b>; choose a
     2215suitable name expressing the particular instrument configuration used in
     2216collecting the calibration data. I named it <b style='mso-bidi-font-weight:
     2217normal'><span style='font-family:"Calibri",sans-serif;mso-ascii-theme-font:
     2218minor-latin;mso-hansi-theme-font:minor-latin'>POWGEN_1066.instprm</span></b> (with
     2219the default extension) to reflect the wavelength band used to collect it on
     2220POWGEN. This completes this tutorial.</p>
     2221
     2222<p class=MsoNormal><o:p>&nbsp;</o:p></p>
    15912223
    15922224</div>

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