[Ifeffit] RE: About Cu2+ xafs

[Scott Calvin]

Hi Igor (and Anatoly),

I could be wrong, but if I recall correctly a self-consistent field 
calculation by FEFF8 [i]calculates[/i] what it thinks E0 should be 
relative to the derivative peak, and then uses that as the "new" 
baseline E0. In other words, a d-E0 found via the SCF FEFF 
calculation is relative to a different starting point! You can figure 
out what the SCF FEFF calculation assigned as the baseline E0 by 
looking at the file xmu.dat and seeing what energy k = 0 corresponds 
to.

--Scott Calvin
Sarah Lawrence College

>
>
>The second problem is of philosophical nature and more important 
>than the first one because its clarification will provide the answer 
>for the first problem and also some peace of mind. I do not 
>understand why the E0 corrections (d_E0's) are so different. The 
>fact that the correction obtained from SCF calculation is larger 
>(and apparently worse) than that obtained from the nSCF calculation 
>(absolute values) seems counter intuitive to me. The E0 value I 
>picked for background subtraction is 8989 eV, and applying the 
>corrections, I find an edge energy of 8990.1 eV and 8981.5 eV 
>respectively.  This second value falls in the pre-edge region, 
>pretty much on the 1s-3d transition bump. Despite the evidences, I 
>tend to trust the SCF's d_E0 value the most but would like to 
>understand the physics (or lack of) behind the different feff 
>calculations!
>
>I apologize if I bored you with unecessary details! Thank you very 
>much for your attention and willingness to help! I really appreciate 
>it!
>
>Best regards,
>
>Igor
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