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