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1980s and 1990s for describing peak shapes from conventional Xray powder diffraction patterns, though it has now been superceded in popularity by the pseudoVoigt peakshape function (described on the next page). The Pearson VII function is basically a Lorentz function raised to a power m:
w^{2m}

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
© Copyright 19972006.
Birkbeck College, University of London.

Author(s):
Paul Barnes Simon Jacques Martin Vickers 