Non-Ideal Data Diffraction in the Real World. Scott A Speakman, Ph.D. [email protected] http://prism.mit.edu/xray. The calculated diffraction pattern represents the ideal X-ray powder sample. The ideal powder sample Millions of grains Randomly oriented grains Flat Smooth surface
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Non-Ideal DataDiffraction in the Real World
Scott A Speakman, Ph.D.
Nanorod along the c-axis
m is the linear mass absorption coefficient for a specific sample
Full asymmetry correction
No asymmetry correction
The crystallographic direction (black arrow) is parallel to the diffraction vector (blue arrow), so the illustrated planes will diffract.
The crystallite is now tilted so that the crystallographic direction (black arrow) is NOT parallel to the diffraction vector (blue arrow), so the illustrated planes will NOT diffract.
Some grains (shaded blue) are oriented in such a way that they do not contribute to any diffraction peak
A small fraction of grains (shaded blue) in this sample are properly oriented to produce the (100) diffraction peak
A different fraction of grains (shaded blue) are properly oriented to produce the (110) diffraction peak
Path measured by a point or X’Celerator detector in a linear diffraction scan
Polycrystalline thin film on a single crystal substrate
Mixture of fine and coarse grains in a metallic alloy
Conventional linear diffraction patterns would miss information about single crystal or coarse grained materials