PseudoVoigt

Description

The Pseudo-Voigt function is an approximation for the Voigt function, which is a convolution of Gaussian and Lorentzian function. It is often used as a peak profile in powder diffraction for cases where neither a pure Gaussian or Lorentzian function appropriately describe a peak.

Instead of convoluting those two functions, the Pseudo-Voigt function is defined as the sum of a Gaussian peak G(x) and a Lorentzian peak L(x), weighted by a fourth parameter \eta (values between 0 and 1) which shifts the profile more towards pure Gaussian or pure Lorentzian when approaching 1 or 0 respectively:

PV(x) = \eta G(x) + (1 - \eta)L(x)

Both functions share three parameters: Height (height of the peak at the maximum), PeakCentre (position of the maximum) and FWHM (full width at half maximum of the peak).

The figure below shows data together with a fitted Pseudo-Voigt function, as well as Gaussian and Lorentzian with equal parameters. The mixing parameter for that example is 0.7, which means that the function is behaving more like a Gaussian.

Comparison of Pseudo-Voigt function with Gaussian and Lorentzian profiles.

Properties (fitting parameters)

Name Default Description
Mixing 1.0  
Height 0.0  
PeakCentre 0.0  
FWHM 0.0  

Categories: FitFunctions | Peak

Source

C++ source: PseudoVoigt.cpp

C++ header: PseudoVoigt.h