I've been trying to get the correct theoretical peak positions [vertical lines] when doing Rietveld refinement for my material.
My material is MIL53ht. I have input all lattice parameters in Full Prof and Powder Cell and as you can see in the first two figures, both software give me the same simulated peak positions (green lines in first figure and green-boxed simulated XRD spectrum in second figure). Even though a comparison between these two figures show consistent peak positions, these do not agree with those found in the literature (third figure; see reference).
I believe I am doing something wrong but I am not sure what it is. The lattice parameters I define are the same as those allegedly used in the literature (reference) to generate the peak bars in the third figure.
What am I doing wrong??
Thank you in advance :)
Referenced Article:
Loiseau, T., Serre, C., Huguenard, C., Fink, G., Taulelle, F., Henry, M., … Férey, G. (2004). A Rationale for the Large Breathing of the Porous Aluminum Terephthalate (MIL-53) Upon Hydration. Chemistry - A European Journal, 10(6), 1373–1382. https://doi.org/10.1002/chem.200305413
Could you send the cel-file?
Did you consider that they used Co radiation instead of the typically used Cu radiation (default setting in PowderCell)?
This may be due to incorrect wavelength (as suggested by Dr. Gert) or space group or lattice parameters used for simulation of diffraction profile. Please check the above parameters.
Dear Dr. Garcia,
first, I want to tell you that your data quality is very poor. if you are still interested to refine the structure then follow the Dr. D. Kumar suggestions. Make sure that, you are using correct wavelength and space group. due to the poor data quality software may not be able to refine lattice parameters, in such situation you can tune lattice parameter values manually and try to get the correct one.
Dear A. R. Garcia, even if we are wrong or our advices are not really helpful, it is our time we are spending for you. Most of us are no native speakers so that some things might sound a bit rude but you should always see the benefit for you. If somebody else did not find an obvious solution for your problem you did not make a simple/stupid mistake. This already helps you...
Regarding the initial problem: I spend some minutes (not more because I also do not have time to solve other persons problems). The structure looks approximately identical...but the peak positions don't which are related to the lattice parameters only. On the other hand, all data I've seen in the paper are those used by you.
However, what I see as problem is the density of the phase. It is lower than water (
Thanks for your kind words, I thought that my suggestions will be helpful for you but I was wrong.
Dear Andrew R Garcia,
Don't worry about the problems. I revisited your attached XRD spectrum. I come to know that there are mismatch (shift) between observed and simulated peaks position as indicated below attached picture of XRD spectrum. This may happen due to smaller or large lattice parameters used during the modelling. Of course, you have used the parameters given in the reference paper. But, in general, lattice parameters vary according to particle size and synthesis conditions. So, slightly decrease or increase the lattice parameters to match the patterns. Use the wavelength of radiation only which is used during XRD measurement. I possible you can attach .dat file of XRD along with details of structural model. If I get time, then try to solve the problem. There may be other things which one can not detect simply by seeing XRD spectrum. And one more thing, please use 5 -10 cycles for refinement rather than 100.
Good luck
The "problem" with your data is the big noise to signal ratio, therefore someone called it "poor". Sometimes it is not changable, however, you should understand that the higher the noise the worse is any interpretation since small peaks cannot contribute anymore to the result. In your case the comparatively huge symbols for the intensity spots possibly also irritate. I know, otherwise it is hard to see them but especially for low signals it becomes difficult to realize what is noise and what is usable signal.
- Badges
- Science topic
- Similar topics
- Correction