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LeBailFit v1

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Summary

Do LeBail Fit to a spectrum of powder diffraction data.

See Also

CreateLeBailFitInput, FitPowderDiffPeaks

Properties

Name	Direction	Type	Default	Description
InputWorkspace	Input	MatrixWorkspace	Mandatory	Input workspace containing the data to fit by LeBail algorithm.
OutputWorkspace	Output	Workspace2D		Output workspace containing calculated pattern or calculated background.
InputParameterWorkspace	Input	TableWorkspace	Mandatory	Input table workspace containing the parameters required by LeBail fit.
OutputParameterWorkspace	Output	TableWorkspace		Input table workspace containing the parameters required by LeBail fit.
InputHKLWorkspace	Input	TableWorkspace	Mandatory	Input table workspace containing the list of reflections (HKL).
OutputPeaksWorkspace	Output	TableWorkspace		Optional output table workspace containing all peaks’ peak parameters.
WorkspaceIndex	Input	number	0	Workspace index of the spectrum to fit by LeBail.
FitRegion	Input	dbl list		Region of data (TOF) for LeBail fit. Default is whole range.
Function	Input	string	LeBailFit	Functionality. Allowed values: [‘LeBailFit’, ‘Calculation’, ‘MonteCarlo’, ‘RefineBackground’]
PeakType	Input	string	ThermalNeutronBk2BkExpConvPVoigt	Peak profile type. Allowed values: [‘ThermalNeutronBk2BkExpConvPVoigt’, ‘NeutronBk2BkExpConvPVoigt’]
BackgroundType	Input	string	Polynomial	Background type. Allowed values: [‘Polynomial’, ‘Chebyshev’, ‘FullprofPolynomial’]
BackgroundParameters	Input	dbl list		Optional: enter a comma-separated list of background order parameters from order 0.
BackgroundParametersWorkspace	InOut	TableWorkspace		Optional table workspace containing the fit result for background.
PeakRadius	Input	number	5	Range (multiplier relative to FWHM) for a full peak.
PlotIndividualPeaks	Input	boolean	False	Option to output each individual peak in mode Calculation.
IndicationPeakHeight	Input	number	0	Heigh of peaks (reflections) if its calculated height is smaller than user-defined minimum.
UseInputPeakHeights	Input	boolean	True	For ‘Calculation’ mode only, use peak heights specified in ReflectionWorkspace. Otherwise, calcualte peaks’ heights.
Minimizer	InOut	string	Levenberg-MarquardtMD	The minimizer method applied to do the fit, default is Levenberg-Marquardt. Allowed values: [‘BFGS’, ‘Conjugate gradient (Fletcher-Reeves imp.)’, ‘Conjugate gradient (Polak-Ribiere imp.)’, ‘Damped GaussNewton’, ‘FABADA’, ‘Levenberg-Marquardt’, ‘Levenberg-MarquardtMD’, ‘Simplex’, ‘SteepestDescent’, ‘Trust Region’]
Damping	Input	number	1	Damping factor if minimizer is ‘Damped Gauss-Newton’
NumberMinimizeSteps	Input	number	100	Number of Monte Carlo random walk steps.
MCSetupWorkspace	Input	TableWorkspace		Name of table workspace containing parameters’ setup for Monte Carlo simualted annearling.
RandomSeed	Input	number	1	Random number seed.
AnnealingTemperature	Input	number	1	Temperature used Monte Carlo. Negative temperature is for simulated annealing.
UseAnnealing	Input	boolean	True	Allow annealing temperature adjusted automatically.
DrunkenWalk	Input	boolean	False	Flag to use drunken walk algorithm. Otherwise, random walk algorithm is used.
MinimumPeakHeight	Input	number	0.01	Minimum height of a peak to be counted during smoothing background by exponential smooth algorithm.
AllowDegeneratedPeaks	Input	boolean	False	Flag to allow degenerated peaks in input .hkl file. Otherwise, an exception will be thrown if this situation occurs.
ToleranceToImportPeak	Input	number	Optional	Tolerance in TOF to import peak from Bragg peaks list. If it specified, all peaks within Xmin-Tol and Xmax+Tol will be imported. It is used in the case that the geometry parameters are close to true values.

Description

This algorithm performs Le Bail fit to powder diffraction data, and also supports pattern calculation. This algorithm will refine a specified set of the powder instrumental profile parameters with a previous refined background model.

Peak profile function for fit

Back to back exponential convoluted with pseudo-voigt

Here is the list of the peak profile function supported by this algorithm.

• Thermal neutron back-to-back exponential convoluted with pseudo-voigt

  • geometry-related parameters: Dtt1, Dtt2, Zero

  • back-to-back exponential parameters: Alph0, Alph1, Beta0, Beta1

  • pseudo-voigt parameters: Sig0, Sig1, Sig2, Gam0, Gam1, Gam2

Thermal neutron back to back exponential convoluted with pseudo-voigt

Here is the list of the peak profile function supported by this algorithm.

• Thermal neutron back-to-back exponential convoluted with pseudo-voigt

  • geometry-related parameters: Dtt1, Zero, Dtt1t, Dtt2t, Width, Tcross

  • back-to-back exponential parameters: Alph0, Alph1, Beta0, Beta1, Alph0t, Alph1t, Beta0t, Beta1t

  • pseudo-voigt parameters: Sig0, Sig1, Sig2, Gam0, Gam1, Gam2

Optimization

LeBailFit supports a tailored simulated annealing optimizer (using Monte Carlo random walk algorithm). In future, regular minimizes in GSL library might be supported.

Supported functionalities

* LeBailFit: fit profile parameters by Le bail algorithm;

* Calculation: pattern calculation by Le bail algorithm;

* MonteCarlo: fit profile parameters by Le bail algorithm with Monte Carlo random wal;

* RefineBackground: refine background parameters

Further Information

See Le Bail fit concept page.

Categories: AlgorithmIndex | Diffraction\Fitting

Source

C++ header: LeBailFit.h

C++ source: LeBailFit.cpp