Split pseudo-Voigt

The method most commonly used consists of considering that each diffraction peak corresponds to two half-Pearson VIIs or two half pseudo-Voigts each one defined on one of the two sides of the peak s maximum. This is called a spht-Pearson VII or a split pseudo-Voigt . The parameters that characterize each of the parts of the profile are independent and the resulting overall function is dissymmetric. 

Figure 3.10. Dissymmetric fitting profile, use of a split pseudo-Voigt...

Peak shape function Pearson VII or split Pearson VII pseudo-Voigt... 

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