Thank Jeremy the feff.inp file and Fourier transformed EXAFS is attached. I fitted the nearest neighbor scattering path, only single scattering Pt and I am sorry, I wrote wrong fitting range Fitting range K-sapce: 3.0 ~ 15 A-1 R -space: 1.3~3.3 A Date: Thu, 12 Jan 2012 16:05:25 -0600 From: kropf@anl.gov To: ifeffit@millenia.cars.aps.anl.gov Subject: Re: [Ifeffit] problem of overestimated E0 (Edge-energy) I think we’ll need more information to help out: at a minimum, the feff.inp file. Also, are you fitting just the nearest neighbor scattering path? To begin to answer your question, while it is often the case that Eo falls below the white line peak, this is not categorically true. A relevant example might be PtO2. Jeremy Chemical Sciences and Engineering Division Argonne National Laboratory Argonne, IL 60439 Ph: 630.252.9398 Fx: 630.252.9917 Email: kropf@anl.gov From: ifeffit-bounces@millenia.cars.aps.anl.gov [mailto:ifeffit-bounces@millenia.cars.aps.anl.gov] On Behalf Of JeongEunSuk Sent: Thursday, January 12, 2012 3:47 PM To: ifeffit Subject: [Ifeffit] problem of overestimated E0 (Edge-energy) Hello all I want to understand EO(edge-energy), precisely. (In Artemis, EO is writed as Enor) Generally, EO is energy when electrons start to go out from core atom in XAFS. As you know, the experiments show that to find EO is not easy in XAFS. To remove background, sometimes I chose EO, the value of the maximum derivative in Athena. and when fitting, the E0 is correted by theoritical FEFF. This is my question. The attached file is the figure of Pt foil(Pt L3 edge measurement). I think edge-enegy has to be in range between A and C because electrons start to move to continum state in that range. However, fitted E0 is shifted to C (about 11573eV). and then when removing background I chose E0=11563eV(This is Pt L3 edge). Fitted E0 is overestimated value, compared with whit line(B). That means the calculated EO obtained from FEFF8.0 (using auto-self consistency field potential) is larg! er than that of experiment. Do I need to change SCF potential in FEFF8.0? ---------------------------------------------------------------------------------------------------------------------------- This is fitting parameters and results(in my case, I used Linux version) To remove background k -range = 2.5 ~ 15, EO=11563eV, Rbkg=1.3, kweight =1 To fit data k -range = 3.0~13.5, R -range =2.3~13.5 1. fitting parameters set macc = 0.0 set so2 = 0.89 // reduction factor guess ePt = 0.0 // energy shift set npt1=1.0 // the number of Pt (1.0 means 12 Pt atoms around core Pt) gu! ess dpt1 = 0.0042 // effective bonding length guess sigpt1=0.005100 //Debye waller factor 2. fitting results fit results, goodness of fit, and error analysis: independent points in data = 8.152 number of variables in fit = 3 degrees of freedom in fit = 5.152 r-factor of fit = 0.002700 chi-square = 1267.097168 ! ; reduced chi-square &nb! sp; = 245.926361 feffit found the following values for the variables: variable best fit value uncertainty initial guess ept = 10.758198 0.860494 4.000000 dpt1 = 0.006462 0.002930 0.004200 sigpt1 = &nbs! p; 0.005114 0.000098 0.005100 correlation between variables variable #1 variable #2 correlation ept dpt1 0.926524 all other correlations are less than 0.25000 --------------------------------------------------------------------------------------------- Because the correlation between E0 and effective bonding length is big, I checked the fit as set bonding and the rest of parameters is variables, and then the result is not changed. That means EO still is big. &! nbsp; _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
