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<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Dear Nick and GSAS
<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">For refinement of silicon you need to make sure that you have the correct setting of the space group. If you download the silicon CIF from ICSD you may have
the space group setting so that silicon atoms are on x = 0 y = 0 z = 0. You need to change this to the other setting so that silicon atoms are on x = 0.125 y = 0.125 z = 0.125. This should give you a much better fit.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Best wishes<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Dr. Tony Bell<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Senior X-ray Technician<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Materials and Research Engineering Institute<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">Sheffield Hallam University<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">City Campus<br>
Howard Street<br>
Sheffield<br>
S1 1WB<o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span lang="EN" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><a href="mailto:Anthony.Bell@shu.ac.uk">Anthony.Bell@shu.ac.uk</a><o:p></o:p></span></p>
<p class="MsoNormal"><span lang="EN" style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">0114
</span><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D">225 3401<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif"">From:</span></b><span lang="EN-US" style="font-size:10.0pt;font-family:"Tahoma","sans-serif""> gsas-ii-bounces@aps.anl.gov [mailto:gsas-ii-bounces@aps.anl.gov]
<b>On Behalf Of </b>Nick Weadock<br>
<b>Sent:</b> 30 August 2017 22:58<br>
<b>To:</b> gsas-ii@aps.anl.gov<br>
<b>Subject:</b> [GSAS-II] Help with refinement of laboratory xray data<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I am attempting to refine diffractograms of the NIST SRM 640c Si standard that I acquired on an Inel CPS120 diffractometer. I was able to successfully get out the instrument parameters using peakfit, and the results are quite good (Rwp
~ 5%). <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">However, I have no success when I try a refinement on the data. The phase data comes from a CIF file, and the calculated reflection positions match fairly well with the peaks in the data. However, the "refined" pattern does not follow
the data at all (Rwp > 54%) and the background is much larger than it should be. I have tried several background functions and have varied the sample displacement parameters and the lattice parameter, but nothing helps. <o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Has anyone experienced a similar situation? Any advice is appreciated. <br clear="all">
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Thanks,<o:p></o:p></p>
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<p class="MsoNormal">-- <o:p></o:p></p>
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<p class="MsoNormal">Nick Weadock<o:p></o:p></p>
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<p class="MsoNormal">PhD Candidate, Materials Science<o:p></o:p></p>
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<p class="MsoNormal">California Institute of Technology<o:p></o:p></p>
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<p class="MsoNormal">1200 E California Blvd, Pasadena, CA 91125<o:p></o:p></p>
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<p class="MsoNormal">MC 138-78<o:p></o:p></p>
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<p class="MsoNormal">x2520<o:p></o:p></p>
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