PDFmorph is a Python software package designed to increase the insight researchers can obtain from measured atomic pair distribution functions (PDFs) in a model-independent way. The program was designed to help a researcher answer the question: Has my material undergone a phase transition between these two measurements?
One approach is to compare the two PDFs in a plot and view the difference curve underneath. However, significant signal can be seen in the difference curve from benign effects such as thermal expansion (peak shifts) and increased thermal motion (peak broadening) or a change in scale due to differences in incident flux, for example. PDFmorph will do its best to correct for these benign effects before computing and plotting the difference curve. One measured PDF (typically that collected under higher temperature) is identified as the target PDF and the second PDF is then morphed by "stretching" (chaning the r-axis to simulate a uniform lattice expansion), "smearing" (broadening peaks through a uniform convolution to simulate increased thermal motion), and "scaling" (self-explanatory). PDFmorph will vary the amplitude of the morphing transformations to obtain the best fit between the morphed and the target PDFs, then plot them on top of each other with the difference plotted below.
There are also a few other morphing transformations in the program.
Finally, we note that PDFmorph should work on other spectra that are not PDFs, though it has not been extensively tested beyond the PDF.
This software is subject to license and copyright restrictions listed here.
PDFmorph is currently run from the command line, which requires opening and typing into a terminal window or Windows command prompt. It is recommended that you consult online resources and become somewhat familiar before using PDFmorph.
PDFmorph requires Python 3 and several third party libraries that are used by PDFmorph and its components.
- NumPy - library for scientific computing with Python
- matplotlib - Python 2D plotting library
- SciPy - library for highly technical Python computing
- diffpy.utils - shared helper utilities for wx GUI
To install these packages, please see installation instructions at their respective web-pages.
To create and activate a conda environment to use this software, run the following command from the command line
conda create -n pdfmorph_env python=3 source activate pdfmorph_env
If you're using Windows, replace source activate pdfmorph with
activate pdfmorph_env
When you are finished with the session, exit the environment by running
source deactivate pdfmorph_env
or
deactivate pdfmorph_env
For your future sessions with the application: Make sure to run the
source activate pdfmorph_env or activate pdfmorph_env commands
from your command line beforehand to ensure access to the software.
Once in your desired conda environment, you can install from either the "diffpy" or "conda-forge" channels of Anaconda packages by running either
conda config --add channels diffpy conda install diffpy.pdfmorph
or
conda config --add channels conda-forge conda install diffpy.pdfmorph
If you don't use Anaconda or prefer to install from sources, please consult online documentation.
With Anaconda, PDFmorph can be later upgraded to the latest released version using
conda update diffpy.pdfmorph
With other Python distributions the program can be upgraded to the latest version as follows
easy_install --upgrade diffpy.pdfmorph
For detailed instructions and full tutorial, consult online documentation.
Once the required software, including PDFmorph is all installed, open up a terminal and check installation has worked properly by running
source activate pdfmorph_env pdfmorph -h #get some helpful information pdfmorph --version
If installed correctly, this last command should return the latest version of PDFmorph. To begin using PDFmorph, run a command like
pdfmorph <target PDF file> <morphed PDF file>
where both PDFs file are text files which contain PDF data, such as those
produced by PDFgetX2, PDFgetX3, or PDFgui. Though some file
extensions other than .cgr, but with the same content structure, have
been shown to work with PDFmorph, it is recommended to stick with .cgr
files such as those in the tutorial.
Enjoy!
PDFmorph is an open-source software project on Github: https://github.com/diffpy/diffpy.pdfmorph.
Feel free to fork the project and contribute! To install PDFmorph in a development mode where the source files are used directly rather than copied to a system directory, use
python setup.py develop --user
For more information on PDFmorph, visit the PDFmorph project web-page, or email Professor Simon Billinge at [email protected]