[GSAS-II] Refining 2D layered materials

[Bartłomiej Gędziorowski]

Dear Dylan,

Probably problem results from the fact that GSAS cannot refine parameter 
a and b, because there are no appropriate reflections. Try to disable 
refining of the unit cell parameters, instead refine hydrostatic/elastic 
strain in Data tab. Select only parameter that corresponds with c (D33 
if I'm correct). At the ned of the refinement you can do Edit 
Phase->Apply strain to lattice constants (also in Data tab).

Regards,
Bartek

W dniu 10.12.2019 o 01:39, Dylan J Bardgett via GSAS-II pisze:
> Dear all,
>
> I am trying to perform Le Bail fits and eventually rietveld 
> refinements on layered 2D heterostructure with known orientations to 
> the substrate. More specifically, my samples are all oriented such 
> that the 001 axis is aligned with the silicon substrate. The 
> diffraction patterns were collected on a lab diffractometer oriented 
> such that only (hk0) reflections will be observed. I have tried 
> experimenting with the preferred orientation parameters, but I get a 
> "Refinement error: invalid metric tensor, cell/Dij refinement not 
> advised" error whenever I try to refine the unit cell with a non-unity 
> March-Dollase ratio. I haven't been able to find any tutorials on 
> refining layered materials in GSAS-II. Does anyone have any suggestions?
>
> Best,
>
> Dylan
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-- 
Bartłomiej Gędzioroski, Ph.D.
AGH University of Science and Technology,
Faculty of Energy and Fuels,
Department of Hydrogen Energy,
al. Mickiewicza 30
30-059 Krakow, Poland