I've been trying to obtain the cell parameters of CeVO4 and SmVO4 from rietveld refinement of XRD data. However the peaks seem to disappear after refining U, V, W parameters in Full-Prof software or any if the parameters in GSAS software. I completed the same with LaVO4 without any of the aforementioned issues. The cif file graph and obtained data are good matches. I was hoping someone would be able to help me with this.
By definition the instrumental parameters (U,V;W) depend on the instrument, not on the specimen...So in principle they should be refined on a standard and then be fixed... So if you collected the data on the same instrument, use the same file obtained for the LaVO4, fix U,V,W and then change La with Ce or Sm. You should get some intensity
Before the U,V,W refinement some intensity was present? The profile parameters reached wrong values that broadened so much the peaks giving the suggestion that the peaks disappeared. Following the suggestion of Matteo Leoni, if the crystallographic model is right, some intensity should be evident.
@Matteo Leoni I found the U, V, W value using cmpr for using with gsas but had the same issue, and the space group of Sm and Ce are tetragonal I41/amd (141) and La is P21/c
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