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
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