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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