I synthesized different oxide nanomaterials but cannot find the Preferred Orientation and Strain of crystal structure. how to resolve it, give me yours valuable suggestion.
All Rietveld programs include terms to describe preferred orientation. Strain (and crystallite size) are often described indirectly by the line profile function. The 2Theta dependence of the FWHM can be interpreted in terms of strain and crystalite size under the condition that the instrumental parameters are well known.
The manuals will give you details of the equations that are used in the various programs. Some Rietveld programs are Fullprof, GSAS-II, Jana, Maud, TOPAZ.
Matteo Leoni and Paolo Scardi published several detailed papers on the effect of size / strain /defects on a powder diffraction pattern.
The implicit assumption of any Rietfeld program is that the structure is periodic. The width of the Bragg reflections is described by convoluting the Bragg reflections with the profile function. This concept breaks down for nanoparticles of very small size (roughly smaller than 5 nm) and in the presence of extensive defects that "ruin" the periodicity. If this is the case for your samples, you will have to calculate the diffraction pattern by use of the Debye-Scattering-Equation. Suitable programs are the Debussy-Suite A. Cervellino et al. ) and my own DiSCUS program. Preferred orientation is a bit more tricky to calculate with DSE, Antonio Cervellino published a few papers on this topic.
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