Powder Diffraction - Spallation Neutron Source

Single Crystal Diffraction Intensities
The Intensity of a diffracted beam, I hkl is related to a complex quantity
called the structure factor, F hkl
– I hkl |F hkl| 2
The structure factor is determined by summing over all atoms in the
crystal:
– F hkl f i exp[2i(hx i + ky i + lz i)] exp(-U iQ 2 /2)
Since adding multiples of 1 to x i,y i or z i does not change the above, the sum
can be simplified to include only the atoms of one unit cell
– f i represents the scattering power of an atom (also used, b i)
– U i represents the average displacement of an atom from its ideal site
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