[Ifeffit] "Hard tests failed in fovrg"
Hi all, I am trying to fit Eu L3 edge EXAFS data of Eu complex whose structure is known (hopefully correct). The default feff6l in Artemis reports an error “Hard tests failed in fovrg. Muffin-tin radius may be too large; coordination number too small“. When I run feff8.2, this error exchanges with the following message “The phase shift correction is accurate to k=19”. I guess that this is not a problem, because my data is until k equal 12 A^-1. However, the fit of the first shell (9O/9N) gives Eo equal to 13, which is unrealistic. This fit with paths calculated with feff6l gives reasonable Eo value. But the phase shifts seem to be calculated incorrectly. I will be very thankful for any hint! Thanks in advance Tonya ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Re: [Ifeffit] "Hard tests failed in fovrg"
On Friday 30 January 2009 08:49:36 am tony vitova wrote: > Hi all, > > I am trying to fit Eu L3 edge EXAFS data of Eu complex whose structure is > known (hopefully correct). The default feff6l in Artemis reports an error > “Hard tests failed in fovrg. Muffin-tin radius may be too large; > coordination number too small“. When I run feff8.2, this error exchanges > with the following message “The phase shift correction is accurate to > k=19”. I guess that this is not a problem, because my data is until k equal > 12 A^-1. However, the fit of the first shell (9O/9N) gives Eo equal to 13, > which is unrealistic. This fit with paths calculated with feff6l gives > reasonable Eo value. But the phase shifts seem to be calculated > incorrectly. I will be very thankful for any hint! Thanks in advance Tonya, A quit bit of googling turned up this useful mailing list post from John Rehr from a couple of years ago about the "Hard test fail" thing in feff6: http://millenia.cars.aps.anl.gov/pipermail/ifeffit/2005-October/002080.html That doesn't answer your question about feff8 however. John or one of his students would be better able to address that, however one might be concerned that Feff has made a bad choice about which electrons to consider as core electrons and which to consider as valence electrons. A bad choice there could confuse teh self-consistency calculation. I think the bottom line is whether the rest of the results besides E0 make physical sense B -- Bruce Ravel bra...@bnl.gov National Institute of Standards and Technology Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 My homepage:http://xafs.org/BruceRavel EXAFS software: http://cars9.uchicago.edu/~ravel/software/exafs/ ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
[Ifeffit] Self absorption Correction
Hi there, I have measured a pure reference compound with high absorber concentration in fluorescence mode (P K-edge XANES). I tried to use the Self absorption correction included in Athena but I don't really understand the results. Fist: Do I have to use the edge step normalized spectrum or the spectrum without normalization ? I tried both and the results of course a quite different. I would rather use the not normalized spectrum. Second: the value "Angel in" is this the angle between the incident beam and the sample surface" and "Angle out" the angle between the sample surface and the detector position? Third: More general- How can I identify a spectrum suffering self absorption? Just comparing the relative peak intensities of total electron yield signal with the fluorescence yield signal ? thanks a lot for your comments, cheers, Jens -- Jens Kruse Institute for Land Use Faculty for Agricultural and Environmental Sciences Rostock University Justus-von-Liebig-Weg 6 18059 Rostock GERMANY Phone: +49(0)381-498 3190 ___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
Re: [Ifeffit] "Hard tests failed in fovrg"
Hi Everyone, If you ever encounter problems like this, please attach a feff.inp so we and others can duplicate and troubleshoot the problem. Thanks. Cheers, John known (hopefully correct). The default feff6l in Artemis reports an error ?Hard tests failed in fovrg. Muffin-tin radius may be too large; coordination number too small???. When I run feff8.2, this error exchanges with the following message ???The phase shift correction is accurate to k=19???. I guess that this is not a problem, because my data is until k equal 12 A^-1. However, the fit of the first shell (9O/9N) gives Eo equal to 13, which is unrealistic. This fit with paths calculated with feff6l gives reasonable Eo value. But the phase shifts seem to be calculated incorrectly. I will be very thankful for any hint! Thanks in advance___ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit
