On 12/19/2016 02:39 PM, Fuxiang Zhang wrote:

Hi, All I have a problem about E0. It seems that E0 has great effect on the R(x) and the fitting. Can anyone explain how Athena automatically find the E0 value from an EXAFS spectrum. Sometimes the value is not at the peak of derivative of u(E), shall it be corrected manually? Thanks

E0 is highly correlated with R because both E0 and R primarily effect the phase of the EXAFS equation. The way I explain the meaning of the delta E0 parameter when I teach an EXAFS course is that it is the parameter that is used to align the wavenumber grid of the theory and the data. That is, you choose an E0 parameter in Athena to set the k grid of the data. Feff does whatever Feff does to choose it's zero of k. While the theory is quite good, it's not perfect, particularly near the Fermi energy. There is nothing that guarantees that Feff's notion of the zero of k is consistent with your choice in Athena. Hence, you need a delta E0 parameter in your fit. And that parameter is highly correlated (in the numerical sense) with R. HTH, B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Science Group at NSLS-II Building 743, Room 114 Upton NY, 11973 Homepage: http://bruceravel.github.io/home/ Software: https://github.com/bruceravel Demeter: http://bruceravel.github.io/demeter/