I have to agree with Matt Newville, that "The overall answer to 'is there a general method for defining MS Debye-Waller Factors' is still no." One of the reasons for this is that there seems to be insufficient information in the experimental spectra, even with temperature dependent data, to determine all the relevant MS DW factors with reasonable accuracy. In my view it is more efficient to fit, not to the DW factors directly, but instead to the much smaller number of spring constants that implicitly define all the MS DW factors. Krappe and Rossner have implemented this with their Bayesian analysis approach [Phys. Rev. B66, 184303 (2002)] with reasonable results. They used the fast recursion approach of Poiarkova and myself [J. Synchrotron Rad. 8, 313 (2001)] to caclulate the MS DW factors from the springs. The recursion method is implemented in FEFF8 to 2nd order, but it is reasonably straightforward to extend it, as Krappe and Rossner have done. An advantage of their Bayesian approach is that one can take advantage of a priori data, such as ab initio calculations of spring constants (e.g., as Grant has described or from other ab initio codes like GAUSSIAN, WASP, etc.) as good starting points in a fit and for calculations of the spring constants that cannot (due the limited information in the data) be fit. Work along these lines is in progress here at UW, which hopefully, will help with the goal "It sure would be nice to have something like this available in ifeffit" J. Rehr