# Differences

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 pawley_refinement_and_background_fitting [2011/08/24 15:02]johnsoevans created pawley_refinement_and_background_fitting [2011/08/25 19:14]alancoelho 2011/08/25 19:14 alancoelho 2011/08/24 18:11 alancoelho 2011/08/24 15:02 johnsoevans created Next revision Previous revision 2011/08/25 19:14 alancoelho 2011/08/24 18:11 alancoelho 2011/08/24 15:02 johnsoevans created Line 3: Line 3: 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: ​macro I_Penalty(c,​ v) ​macro I_Penalty(c,​ v) Line 28: Line 28: ​bootstrap_errors 100 ​bootstrap_errors 100 - Alan + --- //​[[alan.coelho@bigpond.com|Alan Coelho]] 2011/08/25 19:13//