Dear everyone, One of the features of constructing models with Ifeffit is that we are forced to think long and hard about the parameters to use for each path. In particular I have had a great deal of difficulty in deciding how to approach the Debye-Waller factors for with multiple scattering (MS) paths. The ideal approach is to define the D-W factors for the MS paths in terms of the factors for the single scattering paths. That way you add no further variables to the model. But if you think about it you will realise that you cannot simply add all the relevant SS factors up to get a sum for your MS path - it all depends on the geometry, the direction of vibration, correlation of vibrations, etc. Its all a bit tricky for those of us dealing with intense MS paths. So what I am asking is, does anyone know of a general method or approach to define the Debye-Waller factors for MS paths (in terms of SS paths or otherwise)? How do all you Ifeffiters deal with the problem? I've found a few papers that discuss it (listed below) but they generally assume that all vibrations are uncorrelated, which is seldom a realistic situation in continuous solids. Munoz-Paez, A. (2000). Inorganic Chemistry 39(17): 3784-3790. Sakane, H. (1998). Journal of the American Chemical Society 120(40): 10397-10401. Haskel, D. (1998). PhD thesis, University of Washington. (appendix) http://www.aps.anl.gov/xfd/people/haskel/PS/thesis.ps Is there anything out there that I've missed? I'd be particularly interested in anything relating to continuous solids or correlated vibrations. Comments/questions/pearls of wisdom very welcome. Peter Peter Southon Research Fellow - School of Chemistry University of Sydney, NSW 2006, Australia +61 2 9351 4425