Dear Rietvelders

I've a basic question on the Rietveld agreement index S (goodness of fit) . In 
"The Rietveld Method" (ed. R.A. Young) it says in chapter 1.4 "An S value of 
1.3 or less is usually considered to be quite satisfactory. An S value of 1.7, 
for example, probably is a warning that you should look further into the 
reasons and question the adequacy of your model." In the literature, however, 
papers are published quite frequently with considerably larger S values (I'm 
just looking at an Acta Cryst. B paper with S values between 6 and 8.5).

The question is now how strict has the 1.3 limit to be applied, what is the 
"largest acceptable" S value? How does one assess S>1.7 and justify it to 
referees?

I should add that I'm not a follower of the R-value cult but think that the 
most important criterion is chemical and physical plausibility.

Thanks for your advice.

Franz Werner
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