Dear all So far, this forum has been very helpful for me to learn and understand how to fit EXAFS spectra of Mn oxides, thanks everyone for your suggestions. Recently, I am working with Ni k-edge EXAFS and I have kind of similar question as Abhijeet Gaur (Ifeffit Digest, Vol 133, Issue 1), in my case, I am trying to fit EXAFS spectra of Ni(II) sorbed to bacterial biomass and Mn oxides (attached). I followed the Matt suggestions by replacing Ni in place of Mn after running Atoms (birnessite model) to generate feff.inp. I have two questions regarding this: 1) Ni(II) can be surface sorbed and or incorporated into Mn oxide structures. But, I cannot generate paths for this particular r-space. What and how can I edit the feff calculations? (attached). 2) Ni(II) sorp to bacterial biomass via some organic ligands (humic or carboxylic acids): The first shell mainly associates with Ni-O distances, there might be also Ni-C distances in later shells. I am wondering, how can I input the C in atoms or feff calculations? I would be happy to receive your comments. Regards Sathish