Difference between revisions of "Temp"

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These peak profile functions are a [http://en.wikipedia.org/wiki/Voigt_profile pseudo-Voigt] type, combining Gaussian (G) and Lorentzian (L) components.
These peak profile functions are a [http://en.wikipedia.org/wiki/Voigt_profile pseudo-Voigt] type, combining Gaussian (G) and Lorentzian (L) components.


The general Gaussian shape is described by the Cagliotti function
The general Gaussian shape (as a function of angle θ) is described by the Cagliotti function


  Gaussian Profile &asymp; U*tan<sup>2</sup>&theta; + V*tan&theta; + W + P/cos<sup>2</sup>&theta;
  Gaussian Profile &asymp; U*tan<sup>2</sup>&theta; + V*tan&theta; + W + P/cos<sup>2</sup>&theta;

Revision as of 04:44, 2 May 2012

GSAS offers 5 different Constant Wavelength (CW) X-ray profile functions. They are described in detail within the GSAS technical manual (see page 156). 11-BM users are encouraged to use either profile type 3 or type 4.

A quick reference for the various profile type 3 and 4 terms is given below. Users are strongly encouraged to read this section of the manual at least once before (or after) blindly using this guide.

These peak profile functions are a pseudo-Voigt type, combining Gaussian (G) and Lorentzian (L) components.

The general Gaussian shape (as a function of angle θ) is described by the Cagliotti function

Gaussian Profile ≈ U*tan2θ + V*tanθ + W + P/cos2θ

These U, V, W, and P variables match the GU, GV, GW, and GP profile terms you see below.


Constant Wavelength X-ray GSAS Profile Type 3

GU = Gaussian U term GV = Gaussian V term GW = Gaussian W term
GP = Gaussian crystallite size broadening LX = Lorentzian crystallite size broadening LY = Lorentzian strain broadening
S/L = Finger-Cox Axial Divergence S term H/L = Finger-Cox Axial Divergence H term trns = sample transparency
shft = sample displacement stec = anisotropic strain ptec = anisotropic crystallite size
sfec = sublattice anisotropic broadening (stacking faults) LXX = Lorentzian microstrain anisotropy LYY = Lorentzian microstrain anisotropy


Constant Wavelength X-ray GSAS Profile Type 4

GU = Gaussian U term GV = Gaussian V term GW = Gaussian W term
GP = Gaussian crystallite size broadening LX = Lorentzian crystallite size broadening ptec = anisotropic crystallite size
trns = sample transparency shft = sample displacement sfec = sublattice anisotropic broadening (stacking faults)
S/L = Finger-Cox Axial Divergence S term H/L = Finger-Cox Axial Divergence H term eta = mixing factor, from pure Gaussian (0) to pure Lorentzian (1)
SXXX = Stephens anisotropic microstrain broadening SYYY = Stephens anisotropic microstrain broadening SZZZ = Stephens anisotropic microstrain broadening