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pawley_refinement_and_background_fitting [2011/08/24 15:02]
johnsoevans created
pawley_refinement_and_background_fitting [2011/08/24 18:11]
alancoelho
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 As a follow on to a discussion on the Rietveld mailing list regarding how to determine the background in a Pawley Refinement with heavily overlapped peaks. As a follow on to a discussion on the Rietveld mailing list regarding how to determine the background in a Pawley Refinement with heavily overlapped peaks.
  
-Often the background seems unreasonably low or just wrong. The reason is that there'​s a range of intensities+bkg that produce an equivalent fit. Jon Wright pointed to a paper of his that has a neat trick for "​helping"​ the bkg set properly http://​www.oldenbourg-link.com/​doi/​pdf/​10.1524/​zkri.219.12…. ​In consists of adding a penalty that comprise the sum of squares of the intensities. The effect this has is to reduce intensities and to equipartition the intensities such that two identically overlapping peaks  would end up with the same intensity. To do this in TOPAS is as follows:+Often the background seems unreasonably low or just wrong. The reason is that there'​s a range of intensities+bkg that produce an equivalent fit. Jon Wright pointed to a paper of his that has a neat trick for "​helping"​ the bkg set properly http://​www.oldenbourg-link.com/​doi/​pdf/​10.1524/​zkri.219.12…. ​It consists of adding a penalty that comprise the sum of squares of the intensities. The effect this has is to reduce intensities and to equipartition the intensities such that two identically overlapping peaks  would end up with the same intensity. To do this in TOPAS is as follows:
  
 <code topas>​macro I_Penalty(c,​ v) <code topas>​macro I_Penalty(c,​ v)

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