CrystalFieldMultiSpectrum¶

import numpy as np

# Build a reference data set
fun = 'name=CrystalFieldMultiSpectrum,Ion=Ce,Temperatures=(44, 150),ToleranceIntensity=0.1,B20=0.37737,B22=3.9770,B40=-0.031787,B42=-0.11611,B44=-0.12544'
fun += ',f0.f1.FWHM=1.6,f0.f2.FWHM=2.0,f0.f3.FWHM=2.3,f1.f1.FWHM=1.6,f1.f2.FWHM=2.5,f1.f3.FWHM=3,f1.f4.FWHM=1'

# This creates a (empty) workspace to use with EvaluateFunction
x = np.linspace(0, 55, 200)
y = x * 0
e = y + 1
ws = CreateWorkspace(x, y, e)

# The calculated data will be in 'data', WorkspaceIndex=1
EvaluateFunction(fun, InputWorkspace=ws, InputWorkspace_1=ws, OutputWorkspace='data')

# Change parameters slightly and fit to the reference data
fun = 'name=CrystalFieldMultiSpectrum,Ion=Ce,Temperatures=(44, 150),ToleranceIntensity=0.1,Symmetry=C2v,B20=0.37,B22=3.9,B40=-0.03,B42=-0.11,B44=-0.12'
fun += ',f0.f1.FWHM=2,f0.f2.FWHM=2,f0.f3.FWHM=2,f1.f1.FWHM=2,f1.f2.FWHM=2,f1.f3.FWHM=2,f1.f4.FWHM=2'
fun += ',ties=(B60=0,B62=0,B64=0,B66=0,BmolX=0,BmolY=0,BmolZ=0,BextX=0,BextY=0,BextZ=0)'

# (set MaxIterations=0 to see the starting point)
Fit(fun, InputWorkspace='Workspace_0', WorkspaceIndex=1,
                   InputWorkspace_1='Workspace_1', WorkspaceIndex_1=1,
                   Output='fit',MaxIterations=100, CostFunction='Unweighted least squares')
# Using Unweighted least squares fit because the data has no errors.