[Ifeffit] Linear combination analysis

Cammelli Sebastiano Sebastiano.Cammelli at psi.ch
Thu Jun 5 04:32:28 CDT 2008


I study a binary alloy (Fe98.7Cu1.3) where a phase change from bcc to fcc is evident (at the Cu K edge of course) and it depends on the annealing time. I have 4 samples A,B,C,D,  where the A shows a perfect bcc structure, while the D a clear fcc structure. B and C have structure that is a mix between the fcc and bcc. I found very interesting to perform some linear fit simulations using the A and D of the XANES and EXAFS of the samples B and C. so  for instance it is possible to get the xanes of the B sample as linear combinations of A and D according to

BXANES = x*AXANES+(1-x)*DXANES  and for the EXAFS


The simulations work perfectly but:

1-       Of course I expect that x=y (am I wrong?). but this is not true according to the values that the linear fit provide me. There is a small but significant difference as x=48±2% and y=44±2%. Does this difference have any physical meaning? Is the error a bit too small (so should I increase it?)  

2-       For the sample C, I got an amazing simulation adding some noise (0.001), but when I try to export the data (operation: "Write a report") I cannot get the data corrected with the noise (I can get only 6 columns: k, data, fit, residual, sample D, sample A). Is there any way to get the data from the data+noise curve? 


Best regards


Sebastiano Cammelli




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