Re: [sdpd] Indexing

[Armel Le Bail <alb...@cristal.org>]

>Dear all, I'm working with ab initio structure determination, my question 
>is: Is advisable  to fit the diffraction pattern before indexing to 
>achieve more accuracy in the peak positions?

This may depend on the FWHM and step and
statistics.

With high resolution instruments and 4 to 6 steps
above the FWHM (0.04 to 0.06 °2-theta for ~1.5 A
wavelength), the derivative methods should provide
peak positions excellent enough for indexing.

In case of low resolution (FWHM > 0.2 to 0.3 ° 2-theta
for ~1.5 wavelength) and large steps (> 0.03 or 0.04°),
fitting could provide better estimations of the peak position,
however, maybe still not enough excellent for indexing...

Is a fit better for peak position estimation than derivative
method if the statistics is bad ? The answer is : improve
the statistics, anyway...

Best wishes,

Armel



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