Stoichiometry Fluctuation C

Stoichiometry fluctuations are also responsible for a line broadening effect that, with the exception of cubic phases, is also hkl) dependent. The effect on the line profile is directly related to the nature of the fluctuation if the compositional variation is described by a suitable function, e.g. a Gaussian curve, then the resulting peak profile component is also Gaussian and the FT for this effect can be written as  

The Shkl can be treated as refinement parameters, subject to the symmetry restriction of the specific Laue group. For example, for an hexagonal phase  

One can think of several other possible line broadening sources. Expressions for the FT may be analytical but also numerical in some cases, as for the grain 

Guinier, X-ray Diffraction in Crystals, Imperfect Crystals and Amorphous Bodies, Freeman, San Francisco, 1963. Reprinted by Dover, New York, 1994. 

King andL. E. Alexander, X-ray Diffraction Procedures for Polycrystalline and Amorphous Materials, 2nd edn., Wiley, New York, 1974. 

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