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From: Dutta,Rajesh <rd...@dr...> - 2024-08-23 01:10:41
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Dear Dominik, Many thanks for the fruitful hints. It is doable somehow even though it is orthorhombic system on top of cubic. Luckily, our SrFeO2.5 (5.6, 5.65, 15.7A) can be treated as pseudocubic system (rotating 45 deg around c-axis). With this setting a,b axes of SrFeO2.5 become like cubic SrTiO3(3.905A). However, I had to manually build both the SrTiO3 and SrFeO2.5 to match the c-axis and to incorporate elastic constants as well. Please have a look at the attached figure (simulation and experimental data). Let me know your thoughts. Besides that, I have questions: (1) Only multibeam kinematical model takes all the reflections using “surface_hkl=(0,0,1)” where others take only one given (H, K, L). Is there any way to make a list for (H,K,L) so that other model can calculate the XRD for several (H,K,L). I tried to give a list but did not work. (2) Is the relaxation parameter treated as strain/stress here? If not, how can I input in-plane stress or strain? I will try to fit the data and let you know the outcomes. Thanks again, Bye, Rajesh From: Dominik Kriegner <dom...@gm...> Sent: Thursday, August 22, 2024 5:46 AM To: Dutta,Rajesh <rd...@dr...> Cc: xra...@li... Subject: Re: [Xrayutilities-users] XRD-Simulation needs elastic parameters External. Dear Rajesh, Is there a standardized way the elastic parameters are provided in the cif files? If so one could update the parser to allow to read it properly. But likely it's better you define the materials manually. I recommend you to look at https://xrayutilities.sourceforge.io/examples.html#using-the-materials-subpackage I am however afraid I did not include some documentation on how to add the elastic parameters. For this maybe best look at how it is done for the predefined materials in the code https://github.com/dkriegner/xrayutilities/blob/main/lib/xrayutilities/materials/predefined_materials.py Finally I must warn you that I do believe that the pseudomorphic stack was never tested for orthorhombic materials on top of a cubic material. I am almost certain it won't exactly do what you expect. You might be able to help yourself and distort the material as you see fit, but I would not rely on the pseudomorphicstack code to work without changes! cheers Dominik On Thu, Aug 22, 2024 at 2:21 AM Dutta, Rajesh via xrayutilities-users <xra...@li...<mailto:xra...@li...>> wrote: 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<http://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 ------------------------------------- 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/> -------------------------------------------- _______________________________________________ xrayutilities-users mailing list xra...@li...<mailto:xra...@li...> https://lists.sourceforge.net/lists/listinfo/xrayutilities-users |
