Dear All,

I think one should not just say that it is /verbotten /to "subtract" background.
Merci to all replies. I would swallow and 'subtract' if I would not be full.
:-)
Best regards,
Olga

Olga Smirnova wrote:

Andreas Leineweber wrote:
Dear all,

I think one should not just say that it is /verbotten /to "subtract" background. This Verbot should only apply for simple Rietveld refinement without considering the effect of the subtraction in the counting statistics (said before) and not telling it in the publication. But in some case something like background subtraction may be helpful. At least I recall an older work where it was proposed that it may be reasonable to calculate a special R-value considering the background level: Author(s): JANSEN E <http://apps.isiknowledge.com/DaisyOneClickSearch.do?product=WOS&search_mode=DaisyOneClickSearch&db_id=&SID=T2jpIF91p18847FCOP@&name=JANSEN%20E&ut=A1994PB26500006&pos=1>, SCHAFER W <http://apps.isiknowledge.com/DaisyOneClickSearch.do?product=WOS&search_mode=DaisyOneClickSearch&db_id=&SID=T2jpIF91p18847FCOP@&name=SCHAFER%20W&ut=A1994PB26500006&pos=2>, WILL G <http://apps.isiknowledge.com/DaisyOneClickSearch.do?product=WOS&search_mode=DaisyOneClickSearch&db_id=&SID=T2jpIF91p18847FCOP@&name=WILL%20G&ut=A1994PB26500006&pos=3> Source: JOURNAL OF APPLIED CRYSTALLOGRAPHY Volume: 27 Pages: 492-496 Part: Part 4 Published: AUG 1 1994 Times Cited: 19 <http://apps.isiknowledge.com/CitingArticles.do?product=WOS&search_mode=CitingArticles&SID=T2jpIF91p18847FCOP@&db_id=WOS&parentQid=1&parentDoc=15&recid=88169708> References: 21 <http://apps.isiknowledge.com/CitedRefList.do?product=WOS&search_mode=CitedRefList&SID=T2jpIF91p18847FCOP@&db_id=WOS&parentQid=1&parentDoc=15&recid=88169708> Citation Map*Citation Map* <javascript:void();> beta Abstract: Profile and Bragg R values are discussed with respect to different versions of the Rietveld program. The R values calculated from an exemplary neutron diffraction pattern are compared. Results obtained by a modified treatment of background and by a simplified method to decompose an observed pattern into Bragg intensities are presented.


However, I do not have never applied that method and I do not know whether it can be regarded as commonly accepted. At least I don't think that it has been included in any of the present-day major Rietveld programs.

Best regards
Andreas Leineweber

Olga Smirnova wrote:
Dear All,

How is life with conventional R factors when you always have to divide by zero background? Let's have time. Considering a part of the profile without peaks one gets 100% cR. I did not give the agreement factor; I would say those cR with all non-excluded points is incorrect, but cR for
points with Bragg contribution is almost the same!
Do you decrease the Rs by adding the background or do you increase cRs by subtracting the background?

OS

PS I did not ask my supervisor before sending such a mail.







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