|Peak Shape Functions
III. Pearson VII
Pearson VII Function
The Pearson VII function was a popular function during the 1980s and 1990s for describing peak shapes from conventional X-ray powder diffraction patterns, though it has now been superceded in popularity by the pseudo-Voigt peak-shape function (described on the next page). The Pearson VII function is basically a Lorentz function raised to a power m:
where m can be chosen to suit a particular peak shape and w is
related to the peak width. Special cases of this function are that it becomes a
Lorentzian as m → 1 and
approaches a Gaussian as
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Birkbeck College, University of London.