Dear GSAS II developers ans users!
I'm using GSAS II for XRD analysis, thanks to Vadim Volochaev's warm
advice. I found that it is indeed incredibly powerful and very flexible
software. Thanks for the developing with open source!
Now I'm interested in the fitting of Anomalous Small-Angle X-ray
Scattering (ASAXS) data of core-shell bimetallic particles, somewhat
repeating the paper Haug2009 (doi:10.1088/0957-4484/20/50/505705).
How do you think, is it possible to perform this task in GSAS with minor
changes in codebase?
The general small-angle study is already implemented and we have
integrated several 2D images in SASD curves of the same sample for
different photon energies. In general: can I just use sequential fit
over these patterns?
In more detail some questions appeared:
1) Does (anomalous) atomic factors are calculated independently for each
dataset? I have a doubts, since "Anomalous density" shown in SASD >
Substances window seems not to depend on the wavelength (energy).
2) Building of core-shell (spherical) model. As I understand, this
requires two fit models: spheres of first substance (core) and spherical
shells of the second substance.
The addition of form-factors and volumes calculation for spherical shell
seems to be pretty straightforward and I have put them in GSAS code by
adding functions with simple subtraction of spherical FF/vol functions
with different radii.
3) Finally, the model should be the same for all SASD curves, with
changes in data described only by f' and f'' energy dependence. As I can
see, it is impossible to add constraints of equivalence between SASD
fitting parameters like it can be done in XRD analysis, is it? It is
hard for me to estimate the amount of work to implement the SASD
constraints, is it planned or too complex for current codebase state?
Thank you in advance,
Best wishes,
Leon
----
Dr. Leon Avakyan
Ass.Prof. Physics Faculty,
Southern Federal University,
Russia
--
Leon Avakyan
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