[Ifeffit] (no subject)

[Bruce Ravel]

On Wednesday, March 13, 2013 08:24:41 PM davood dar wrote:
> 1. *    1*.        What is the ideal value of R- factor for any fit.

R-factor is a way of expressing percentage misfit.  Smaller is
generally better, although smaller is not better if other aspects of
the fit are not defensible.  For instance, if one of the fitting
parameters is physically unreasonable, then getting a smaller R-factor
is not so useful.

R-factor is just one of the ways that the quality of the fit is
evaluated.

I discuss in some detail the statistical parameters reported by the
software here:

  https://speakerdeck.com/bruceravel/advanced-topics-in-exafs-analysis

> 2.  *    2.  * Can we use (fit) the theoretical model generated from square
> pyramidal structure to EXAFS  data of  octahedral structure by assigning
> degeneracy of 2 for the apical atom. OR using octalhedral for square planar
> by not using apical path

Making clever use of Feff calculation on known structures to
investigate unknown structures is something I talk about in 

  https://speakerdeck.com/bruceravel/modeling-non-crystalline-samples

Lots more information at

  http://xafs.org

and at

  http://bruceravel.github.com/demeter/

B


-- 

 Bruce Ravel  ------------------------------------ bravel at bnl.gov

 National Institute of Standards and Technology
 Synchrotron Methods Group at NSLS --- Beamlines U7A, X24A, X23A2
 Building 535A
 Upton NY, 11973

 Homepage:    http://xafs.org/BruceRavel
 Software:    https://github.com/bruceravel