diffpy.srreal package

Tools for real space structure analysis.

Submodules

diffpy.srreal.atomradiitable module

diffpy.srreal.attributes module

diffpy.srreal.bondcalculator module

diffpy.srreal.bvparameterstable module

diffpy.srreal.bvscalculator module

diffpy.srreal.eventticker module

diffpy.srreal.overlapcalculator module

diffpy.srreal.pairquantity module

diffpy.srreal.parallel module

diffpy.srreal.pdfbaseline module

diffpy.srreal.pdfcalculator module

diffpy.srreal.pdfenvelope module

diffpy.srreal.peakprofile module

diffpy.srreal.peakwidthmodel module

diffpy.srreal.scatteringfactortable module

diffpy.srreal.sfaverage module

Compositional averaging of atom scattering factors.

Examples

import numpy as np
from diffpy.srreal.scatteringfactortable import SFTXray
xtb = SFTXray()
qa = np.linspace(0, 25)
sfavg1 = SFAverage.fromComposition({'Na' : 1, 'Cl' : 1}, xtb, qa)
sfavg2 = SFAverage.fromComposition([('Mn', 1), ('O', 2)], xtb, qa)

from diffpy.structure import loadStructure
from diffpy.srreal.pdfcalculator import DebyePDFCalculator
dpdfc = DebyePDFCalculator()
dpdfc(loadStructure('rutile.cif'))
sfavg3 = SFAverage.fromStructure(dpdfc.getStructure(),
                                 dpdfc.scatteringfactortable, dpdfc.qgrid)

class diffpy.srreal.sfaverage.SFAverage[source]

Bases: object

Calculate compositional statistics of atom scattering factors.

Compositional averages can be calculated for an array of Q-values. Results are stored in the class attributes.

f1sum: Sum of scattering factors from all atoms. Float or NumPy array.

f2sum: Sum of squared scattering factors from all atoms. Float or NumPy array.

count: Total number of atoms. Can be non-integer in case of fractional occupancies.

f1avg: Compositional average of scattering factors. Float or NumPy array.

f2avg: Compositional average of squared scattering factors. Float or NumPy array.

composition: Dictionary of atom symbols and their total abundance.

composition = None

count = 0

f1avg = 0

f1sum = 0

f2avg = 0

f2sum = 0

classmethod fromComposition(composition, sftb, q=0)[source]

Calculate average scattering factors from atom concentrations.

Parameters:

composition (dictionary or a list of (symbol, amount) pairs.) – The chemical composition for evaluating the average. Atom symbols may repeat when it is a list of (symbol, amount) pairs.
sftb (ScatteringFactorTable or str) – The ScatteringFactorTable object for looking up the values. When string use ScatteringFactorTable.createByType to create a new lookup table of the specified type.
q (float or NumPy array (optional)) – The Q value in inverse Angstroms for which to lookup the scattering factor values.

Returns:

The calculated scattering factor averages.

Return type:

SFAverage

classmethod fromStructure(stru, sftb, q=0)[source]

Calculate average scattering factors from a structure object.

Parameters:

stru (diffpy Structure or pyobjcryst Crystal or StructureAdapter) – The structure object that stores the atom species and their occupancies. Can be any type with a registered conversion to the StructureAdapter class.
sftb (ScatteringFactorTable or str) – The ScatteringFactorTable object for looking up the values. When string use ScatteringFactorTable.createByType to create a new lookup table of the specified type.
q (float or NumPy array (optional)) – The Q value in inverse Angstroms for which to lookup the scattering factor values.