Thank you for your replies, Anatoly and Matt. As suggested, I've attached a zipped folder with 2 fits that differ only in kmin. You'll notice that the fit improves as kmin is increased. I've also attached the raw data in an Athena file in the event that anyone would like to look at that. Thanks again. ----- Original Message ----- From: ifeffit-request@millenia.cars.aps.anl.gov To: ifeffit@millenia.cars.aps.anl.gov Sent: Monday, December 3, 2012 1:00:01 PM Subject: Ifeffit Digest, Vol 118, Issue 2 Send Ifeffit mailing list submissions to ifeffit@millenia.cars.aps.anl.gov To subscribe or unsubscribe via the World Wide Web, visit http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit or, via email, send a message with subject or body 'help' to ifeffit-request@millenia.cars.aps.anl.gov You can reach the person managing the list at ifeffit-owner@millenia.cars.aps.anl.gov When replying, please edit your Subject line so it is more specific than "Re: Contents of Ifeffit digest..." Today's Topics: 1. Re: S02 and k_min (Anatoly I Frenkel) 2. Re: S02 and k_min (Matt Newville) ---------------------------------------------------------------------- Message: 1 Date: Sun, 2 Dec 2012 18:13:14 +0000 From: Anatoly I Frenkel To: XAFS Analysis using Ifeffit Subject: Re: [Ifeffit] S02 and k_min Message-ID: <545F89325F51764C902D37B42C9F4D5313625DAE@YUWEXCPM12.yuad.uds.yu.edu> Content-Type: text/plain; charset="us-ascii" Michael, If you use the same kmin for the standard and the unknown you will minimize the ambiguity. Anatoly ----- Reply message ----- From: "Michael Morrill" To: "ifeffit@millenia.cars.aps.anl.gov" Subject: [Ifeffit] S02 and k_min Date: Sun, Dec 2, 2012 1:02 PM Hello everyone, I am currently performing a simple curve fit on bulk MoS2 using an atoms file for crystalline MoS2. I've found that increasing k_min on my fit (e.g. from 2 to 4) improves the quality of the fit (R-factor from 0.028 to 0.009), but also increases S02. If I use a large enough k_min (but not so large I run out of data), S02 gets as high as 1.2 +/- 0.05. This trend is observable for single and multiple k-weight fittings. While I understand that S02>1.0 does not necessarily invalidate the fit, I am not sure how to justify which parameter values are the best seeing that "0.8http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit