Difference between revisions of "Temp"
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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. | 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 | 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 GSAS manual at least once before (or after) blindly using this guide! | ||
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. | ||
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These U, V, W, and P variables match the GU, GV, GW, and GP profile terms you see below. | These U, V, W, and P variables match the GU, GV, GW, and GP profile terms you see below. | ||
11-BM users will '''not''' (usually) need to change or refine these values. | |||
Revision as of 04:47, 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 GSAS 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.
11-BM users will not (usually) need to change or refine these values.
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 |
