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RefinePowderDiffProfileSeq v1

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Summary

Refine powder diffractomer profile parameters sequentially.

See Also

RefinePowderInstrumentParameters

Properties

Name

Direction

Type

Default

Description

InputWorkspace

Input

MatrixWorkspace

Name of data workspace containing the diffraction pattern in .prf file.

WorkspaceIndex

Input

long

0

Spectrum (workspace index starting from 0) of the data to refine against in input workspace.

SeqControlInfoWorkspace

InOut

TableWorkspace

Name of table workspace containing sequential refinement information.

InputProfileWorkspace

Input

TableWorkspace

Name of table workspace containing starting profile parameters.

InputBraggPeaksWorkspace

Input

TableWorkspace

Name of table workspace containing a list of reflections.

InputBackgroundParameterWorkspace

Input

TableWorkspace

Name of table workspace containing a list of reflections.

StartX

Input

number

0

Start X (TOF) to refine diffraction pattern.

EndX

Input

number

0

End X (TOF) to refine diffraction pattern.

FunctionOption

Input

string

Refine

Options of functionality. Allowed values: [‘Setup’, ‘Refine’, ‘Save’, ‘Load’]

RefinementOption

Input

string

Random Walk

Options of algorithm to refine. Allowed values: [‘Random Walk’]

ParametersToRefine

Input

str list

List of parameters to refine.

NumRefineCycles

Input

long

1

Number of refinement cycles.

ProfileType

Input

string

Type of peak profile function. Allowed values: [‘’, ‘Neutron Back-to-back exponential convoluted with pseudo-voigt’, ‘Thermal neutron Back-to-back exponential convoluted with pseudo-voigt’]

BackgroundType

Input

string

Type of background function. Allowed values: [‘’, ‘Polynomial’, ‘Chebyshev’, ‘FullprofPolynomial’]

FromStep

Input

long

-1

If non-negative, the previous code is not set from last step, but the step specified.

OutputProjectFilename

Input

string

Name of sequential project file. Allowed extensions: [‘.nxs’]

InputProjectFilename

Input

string

Name of sequential project file. Allowed extensions: [‘.nxs’]

ProjectID

Input

string

Project ID.

Description

The purpose of this algorithm is to provide users a tool to control the workflow to refine powder diffractometer’s peak profile. For Time-Of-Flight powder diffractometers in SNS, back-to-back exponential convoluted with pseudo-voigt profile functions are used. The function is complicated with strong correlated parameters. Thus, the refinement on these parameters contains multiple steps, within each of which only a subset of profile parameters are refined.

In order to control the workflow, there are four major functions supported by this algorithm

Setup  : set up a few workspaces that will be used to refine profile parameters in multiple steps;

Refine  : select a subset of peak parameters and do Le Bail fit on them;

Save  : save the current refinement status and refinement history to a project file;

Load  : set up a few workspaces used for refining by loading them from a previously created project file.

Input and output workspaces

- InputWorkspace : data workspace containing the diffraction pattern to refine profile parameters with;

- SeqControlInfoWorkspace : table workspace used to track refinement. Below is the introduction on the fields/columns of this workspace.

  • Step : refinement step. User can start a refinement from the result of any previous step;

  • OutProfile : name of the table workspace containing refined profile parameters;

  • OutReflection : name of the table workspace containing Bragg peaks’ peak parameters calculated from refined parameters value;

  • OutBackgroud : name of the table workspace containing the value of the output background parameter;

  • OutBckgroundParam : name of the output background parameters;

  • Refine : profile parameters that are refined in this step;

  • RwpOut : output Rwp from refinement;

  • LastStep : last step where this step is based on;

  • RwpIn : input Rwp

  • InProfile : input profile parameter workspace’s name;

  • InReflection : input Bragg peak parameters workspace’ name;

  • InBackgroud : input background workspace;

  • InBckgroundParam : input background parameters.

- InputProfileWorkspace : table workspace contraining starting values of profile parameters;

- InputBraggPeaksWorkspace : table workspace containing the Bragg peaks’ information for Le Bail fit;

- InputBackgroundParameterWorkspace : table workspace containing the background parameters’ value

Supported peak profiles

- Neutron Back-to-back exponential convoluted with pseudo-voigt : Fullprof profile 9 and GSAS TOF profile 3;

- Thermal neutron Back-to-back exponential convoluted with pseudo-voigt: Fullprof profile 10 (a.k.a. Jason Hodges function).

Supported background types

- Polynomial

- Chebyshev

- FullprofPolynomial

Hint for using

This is just a brief description for how to use this algorithm.

  1. Setup;

  2. Refine: refine Dtt1 and Zero from step 0;

  3. Refine : reifne Alph0  and  Beta0  from step 1;

  4. Refine : refine Alph1  from step 1 with failure;

  5. Refine : refine Beta1  from step 1 because step 2 fails;

  6. Refine : refine Sig-1  from last step;

  7. Save : save current work and history to a Nexus file.

Categories: AlgorithmIndex | Diffraction\Fitting

Source

Python: RefinePowderDiffProfileSeq.py