[Xrayutilities-users] XRD-Simulation needs elastic parameters

[Dutta,Rajesh <rd...@dr...>]

Dear xrayutilities users,

I am very new to this tool. I am trying to build a layer stack of Sr2Fe2O5 (ortho) on top of SrTiO3 substrate (cubic). I managed to construct the model using cif files. However, in the cif file seemingly it is not possible to incorporate cij (elastic parameters). Therefore, the fitting XRD gives an error saying "layer' argument needs elastic parameters.

How to solve this issue while importing cif files. I attach few parts of the code below:

# global parameters
wavelength = xu.wavelength('CuKa1')
offset = -0.00  # angular offset of the zero position of the data

# set up LayerStack for simulation: SrTiO3/SrFeO2.5
Sr = xu.materials.elements.Sr
Ti = xu.materials.elements.Ti
O = xu.materials.elements.O
Fe = xu.materials.elements.Fe
STO = xu.materials.Crystal.fromCIF(os.path.join("data", "STO.cif"))
SFO = xu.materials.Crystal.fromCIF(os.path.join("data", "Sr2Fe2O5-along.cif"))

lSTO = xu.simpack.Layer(STO, inf)
lSFO = xu.simpack.Layer(SFO, 800, relaxation=0)

pstack = xu.simpack.PseudomorphicStack001('list', lSTO, lSFO)

# set up simulation object
thetaMono = arcsin(wavelength/(2 * xu.materials.Ge.planeDistance(2, 2, 0)))
Cmono = cos(2 * thetaMono)
dyn = xu.simpack.DynamicalModel(pstack, I0=1.5e5, background=0,
                                resolution_width=2e-3, polarization='both',
                                Cmono=Cmono)
fitmdyn = xu.simpack.FitModel(dyn)
fitmdyn.set_param_hint('SFO_a', vary=True, min=15.7, max=15.8)
fitmdyn.set_param_hint('STO_a', vary=True, min=3.90, max=3.91)
fitmdyn.set_param_hint('resolution_width', vary=True)
params = fitmdyn.make_params()

I tried to build the materials using Crystal class and SGLattice, there I can define elastic tensors but it does not account proper Wyckoff positions, this is why I used cif files.

Any help, please let me know if you need more info.

Thanks,
Rajesh

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Dr. Rajesh Dutta
Research Staff Scientist
Drexel University College of Engineering
Pronouns: he/his/him

Drexel University
3100 Market Street
Philadelphia, PA 19104
drexel.edu<http://drexel.edu/>
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