[Ifeffit] delr and ss parameterization

Hi everyone, I am working with bulk and nano structures of MnO, MnO2 and Mn2O3. I have two questions regarding how to parameterize delr and ss in Artemis. It is recommended to use either delr=alfa*Reff or relate it to unit cell structure. Can anybody tell me how to do the second approach? Also is that a good idea to let all ss to float? Or it should be constrained based on type and distance of atoms? I have seen an example about ZnO just letting the first two shell’s ss to float and let the rest to be the same. I would appreciate it very much if anybody could help me with this too. Regards, Ebrahim Rezaei PhD Candidate, Chem. Eng. Dep., University of Saskatchewan Saskatoon, SK, Canada