[Ifeffit] The most important fitting parameters
b.ingham at irl.cri.nz
Fri Jun 16 08:26:54 CDT 2006
I am trying to use EXAFS, along with other techniques, to attempt to find
information about an unknown structure. It is an organic-inorganic hybrid
material, EDX reveals Cu1-W1-O4 as the stoichiometry of the inorganic
component, which we are most interested in structurally. We have not been
able to solve the structure from XRD, although not for want of trying.
I started off with CuWO4 as the model compound and constrained the fitting
- take all 1st oxygen shells (x6 at slightly different distances) and give
them all amp1, dr1*reff, enot and ss1
- take all 1st copper shells (x2) and give them both amp2, dr2*reff, enot
- take all 2nd oxygen shells (x6), amp3, dr3*reff, enot, ss3
- take all 1st tungsten shells (x6), amp4, dr4*reff, enot, ss4
This gave me 13 parameters with 14.8 independent points.
(Other factors: fitted in kw=2&3, k-range 2-9, used Athena with default
background subtraction parameters as the chi(k) from that seemed sensible.
The data were collected at SSRL, beamline 11-2, in transmission.)
I was happy with the final result (R-factor 0.014), but am just wondering if
this is a sensible way to go about doing things - bearing in mind I am not
sure of the structure in the first place. Any hints or advice would be much
appreciated. I should have collected data at the tungsten edge as well, as
it is not that much higher in energy from Cu, but this didn't occur to me
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