pyXPB is a utility to calculate and visualise powder diffraction profiles and the associated Debye-Scherrer rings in simple material systems. A detector (monochromatic area detector or energy dispersive detector array) and the experimental setup are defined before materials are 'added'. Multiple materials (or phases) can be introduced with a weight factor, which corresponds to the volume fraction of that material/phase.

A strain tensor can be defined and applied to the material(s). There is currently no option to apply a different strain state to each material/phase and no plan to implement this (until needed!).

If we consider a monochromatic x-ray source and a standard flat panel (area) detector then we will need to import MonoDetector and properly define the parameters and experiment (remembering lengths are in mm and energy in keV).

>> from pyxpb.detectors import MonoDetector
>> mono = MonoDetector(shape=(2000,2000), pixel_size=0.2, 
                       sample_detector=700, energy=100, 
                       energy_sigma=0.5)

If we want to work with an 80% Fe, 20% Cu mix, then we could calculate and vizualise the 1D diffraction profile using the add_peaks and plot_intensity commands. The background argument allows you to add an amount of noise relative to the maximum peak height - the impact of this can be seen in the 'total' line profile. The intensity profile extraction/plotting can be done at any arbitrary azimuthal angle (phi) - this is particularly useful when the material is subject to a strain.

>> mono.add_peaks('Fe', weight=0.8)
>> mono.add_peaks('Cu', weight=0.2)
>> mono.plot_intensity(phi=np.pi/2, background=0.01, strain_tensor=(0,0,0))

When interacting with an area detector it is also possible to vizualise the full Deby-Scherrer rings. In this case, we have applied a strain to the material.

>> mono.plot_rings(strain_tensor=(0.2, 0.2, 0.05)

Note that the intensity factor calculations that underpin the profile calculations can be vizualised using the intensity_factor command (and a specified material/phase)

>> mono.intensity_factors('Fe', plot=True))

If you need to access the 1D/2D intensity data the 'intensity' and 'rings' methods can be called:

>> mono.intensity(phi=np.pi/2, background=0.01, strain_tensor=(0,0,0))
>> mono.rings(strain_tensor=(0.2, 0.2, 0.05)

pyxpb is built on Python’s scientific stack (numpy, scipy, matplotlib). Testing and development were carried out using the Anaconda scientific Python distribution (v 4.1), which built with the following packages:

• Python: version 2.7.11 and 3.5.1
• numpy: version 1.10.4
• scipy: version 0.17
• matplotlib: version 1.5

Compatability is expected with earlier versions of Python, numpy, scipy and matplotlib but this has not been tested.

You can install pyxpb from source using the setup.py script. The source is stored in the GitHub repo, which can be browsed at:

https://github.com/casimp/pyxpb

Simply download and unpack, then navigate to the download directory and run the following from the command-line:

python setup.py install