Jatin, IF the uniform expansion model is valid for single scattering paths, then it is for multiple scattering paths as well. For some materials, particularly those with cubic space groups, that's got a good chance of being a useful model. Others tends to distort with changes in temperature, doping, etc., and it may not work as well. But even in those cases, if you've decided how to constrain the delr for single- scattering paths, you'll do reasonably well by using some kind of appropriate average of the delr's for related single-scattering paths. --Scott Calvin Sarah Lawrence College On Oct 7, 2010, at 3:05 AM, Jatinkumar Rana wrote:

Dear all,

It is reasonable to assign a constant fraction by which unit cell expands at a given temperature of XAFS measuremnt and so the variation in the path lengths for every single scattering paths could be assigned as delr = alpha * Reff. Similarly, one can assign sigma2 value for each single scattering path depending on both type of scatterer and its distance from the absorbing atom.

Now coming to multiple scattering paths, Sigma2 for multiple scattering paths can be constrained based on the sigma2 of related single scattering paths and a definite path-geometry-dependent scheme (Triangle, collinear, reversed etc.) could be applied.

Is there any such scheme for delr of multiple scattering paths ? or we can simply assume that all paths (single scattering and multiple scattering) undergo uniform expansion by a factor alpha.

Thank you so much in advance for your valuable time...

With best regards, Jatin Rana _______________________________________________ Ifeffit mailing list Ifeffit@millenia.cars.aps.anl.gov http://millenia.cars.aps.anl.gov/mailman/listinfo/ifeffit