On Friday 23 February 2007 16:24, hw26@njit.edu wrote:
I am doing model fitting using Artemis. My sample is uranium solution with an ionic liquid, 1-methoxyethyl-3-methyl imidazolium tetrafluoroborate (MOEMIMBF4). The Fitting seems ok except that the ss_2 is negative. I don't know how can I fix this problem. Can you get a chance to take a look? My fitting is simple, only three single scattering pathes which were produced by Six Pack. The fitting file is attached. I really appreciate it if you could take a look and give some advice!
Let me ask you a couple questions that I think are closely related to yours. You seem to be modeling an uranyl ligand and two equatorial ligands. Focussing on the second path, the one with a negative sigma^2 and the one that (I am guessing) represents either a hydration shell or a bidentate ligand: 1. Is 35.996 a reasonable value for e0? 2. Is 2.59 Angstrom a reasonable value for an equatorial oxygen ligand in a uranyl moiety? It would seem that your fit has quite a few problems beyond the sigma^2 value. I question whether your parameterization of these three paths is physically defensible. B -- Bruce Ravel ---------------------------------------------- bravel@anl.gov Molecular Environmental Science Group, Building 203, Room E-165 MRCAT, Sector 10, Advanced Photon Source, Building 433, Room B007 Argonne National Laboratory phone and voice mail: (1) 630 252 5033 Argonne IL 60439, USA fax: (1) 630 252 9793 My homepage: http://cars9.uchicago.edu/~ravel EXAFS software: http://cars9.uchicago.edu/~ravel/software/