A couple of thoughts...

A) If I were approaching a problem like this, I would probably prepare a series of samples with different ratios, and look for trends in the fits. If you see consistent differences across the series, in the same direction, you can probably be more confident in the resulting fits, and in your conclusions.

B) This problem seems like it might be a good application of a wavelet transform for analysis. I've been meaning to do some wavelet analysis myself, but haven't gotten around to it, so I can't offer specific advice...But perhaps someone on the list can.


Cheers,



Mike









On Fri, Feb 8, 2019 at 2:37 AM Chongchong Mellon <mellonchongchong@gmail.com> wrote:

Hi all,

 I have some problems in analyzing the EXAFS of solid-solution alloy, let us define as A0.5B0.5. I have searched the mailbox but cannot find similar discussion yet. So I post the question here and hope to get some suggestion from you.


  1. A and B are immiscible metals from the phase diagram, which means that I couldn’t get the bulk A0.5B0.5 as a standard reference. In this case, how can I estimate the amp for the K-edge of A or B? 
  2. A and B are very near (atomic number B-A = 2) in the periodic table. So their lattice parameters are quite close to each other. In this case, when I tried to fit the 1st shell use A-A and A-B paths at the same time, the Happiness parameter becomes worse and the coordination number of A-B is not realistic (large errors!).  If I fit with only the A-A path or A-B path, I get a good fit. However, atomic resolution STEM-EDX maps show the homogenous distribution of both A and B atoms. The A-A and A-B bond might have an equal ratio. In this case, how can I do the fitting?


Thank you very much in advance!


Sincerely,

Chong

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