[GSAS-II] Fourier difference maps

[Toby, Brian H.]

Matias, 

  GSAS-II will compute several types of Fourier maps. These work from the reflection intensities in a selected phase. They will give you information about extra or missing scattering density in that phase, but will not provide any information on an unindexed impurity, which necessarily will have its reflections in different positions. Even if you have the the impurity phase indexed, you usually need a partial structure before you can use Fourier techniques. The one exception would be a Patterson map, which can be helpful in a heavy atom structure, but Pattersons are not commonly used with powders.

Brian

> On Aug 10, 2022, at 10:33 AM, Daniel de Almeida, Matias via GSAS-II <gsas-ii at aps.anl.gov> wrote:
> 
> Hello,
> 
> I am looking to determine an impurity that I have in my sample and am looking into the fourier difference map functionality of GSAS 2. However I was not able to find any tutorials of resources with more information about all the information that the fourier map controls provides. I gather that the delt-F function gives the difference in fourier map of the model and the experimental dataset, but would like to know what other information is possible to be obtained from it. Ideally aside from the atomic coordinates of the impurities, if the elements present at those positions could be given it would help my search for the impurity greatly. 
> 
> I appreciate any resources or help that you can provide.
> 
> respectfully,
> 
> Matias
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