On 07/01/2014 10:43 AM, ZHAN Fei wrote:
1 In the example,multiplet scattering path comes from two model respectively,if use path from different model in different shell's fit,there is risk of ignore important multiple path across models.Should construct a cluster ,run feff to ensure?
I don't completely understand the question, but I'll give it a try. In the example of Shelly's paper, she had a situation where she *couldn't* write a single feff.inp file. Her local environment was the average of all possible ways that the uranyl ion could bond to biomass. The uranyl binding disproportionated into a pH-dependent mixture of carboxyl, phosphoryl, and hydroxyl sites. There was simply no way to write a feff.inp file for that. So her solution was to run Feff more than once, picking and choosing paths that represented her best guess for modeling the average bonding environment. I think what you are really getting at, though, is whether it was right for Shelly to use parts of Feff calculations on a crystals to model something else. If you were to read up on the theory used in Feff, you would find that the important thing is that the muffin tin radii of the scatterers get calculated reasonably. Unless Shelly had a reason to think that the interatomic distances in her biomass sample were VERY different than in the crystals she used to run Feff, then the scattering amplitudes and phase shifts were almost certainly computed quite well enough.
2 I have confusion of the relationship pf N between single path and multiple path,for example I think U-Oe-C U-Oe-Pshould be 1 2 respectively,instead 2 4 in paper.
I think Scott's explanation is correct. In real-space, multiple-scattering theory, both ways around a three-legged path have to be counted. B -- Bruce Ravel ------------------------------------ bravel@bnl.gov National Institute of Standards and Technology Synchrotron Science Group at NSLS --- Beamlines U7A, X24A, X23A2 Building 535A Upton NY, 11973 Homepage: http://xafs.org/BruceRavel Software: https://github.com/bruceravel