X-ray Diffraction: Why Are Peaks of Different Intensities?

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SUMMARY

X-ray diffraction (XRD) produces graphs with peaks that correspond to the crystallographic structure of the sample. The intensity of these peaks varies due to the angular dependence of the atomic form factor, which explains why the (110) peak in body-centered cubic (bcc) structures is the most prominent. Additionally, in samples with multiple elements, differing atomic form factors contribute to the variation in peak intensities. This phenomenon is crucial for interpreting XRD results accurately.

PREREQUISITES
  • Understanding of X-ray diffraction principles
  • Familiarity with Miller indices in crystallography
  • Knowledge of atomic form factors
  • Basic concepts of crystal structures, particularly body-centered cubic (bcc)
NEXT STEPS
  • Research the concept of atomic form factors in X-ray diffraction
  • Study the role of Miller indices in peak intensity analysis
  • Explore the structure factor and its impact on diffraction patterns
  • Investigate the effects of multi-element minerals on XRD peak intensities
USEFUL FOR

Researchers in materials science, crystallographers, and anyone involved in analyzing X-ray diffraction data for material characterization.

abcdmichelle
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This is not really a homework question but a more general plea for an explenation from someone! :)

In x-ray diffraction, you get a graph with different peaks that are particular to the composition of your sample. But, why are some peaks are of higher intesities then others? What is it about the sample/crystal structure that makes some peaks greater then other at certain angles?

thank you!
 
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The intensity falls off with an increasing angle of diffraction (corresponding to larger Miller indices) due to the angular dependence in the atomic form factor. That is why the peak for (110) in bcc is the largest. It is briefly discussed on Wikipedia on the "Structure factor" page, but you can also find it discussed in books.

Also, if the mineral is not monotonic (more than one element), then different elements can have different form factors leading to varying intensities.
 

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