diffpy.srreal 1.4.0

Calculators for PDF, bond valence sum, and other quantities based on atom pair interaction.

Calculators for PDF, bond valence sum, and other quantities based on atom pair interaction.

The diffpy.srreal package provides calculators for atomic pair distribution function (PDF), bond valence sums (BVS), atom overlaps for a hard-sphere model, bond distances and directions up to specified maximum distance. The atomic structure models are represented with internal classes as non-periodic, periodic or structures with space group symmetries. The package provides implicit adapters from diffpy.structure classes or from Crystal or Molecule objects from pyobjcryst. Adapters can be easily defined for any other structure representations in Python allowing their direct use with the calculators. Calculators support two evaluation models - BASIC, which performs a full pair-summation every time, and OPTIMIZED, which updates only pair contributions that have changed since the last evaluation. Calculations can be split among parallel jobs using Python multiprocessing package or any other library that provides parallel map function. PDF calculations can be done in two modes - either as a real-space summation of peak profiles (PDFCalculator) or as a reciprocal-space Debye summation and Fourier transform of the total scattering structure function (DebyePDFCalculator).

The diffpy.srreal package is a Python binding to the C++ library libdiffpy (https://github.com/diffpy/libdiffpy). Calculators are created as objects of a given calculator type and so multiple instances of the same calculator type can exist with different configurations. Calculators are composed of other objects that perform lower-level tasks, such as calculating peak profile or looking up atom scattering factors. These objects can be re-assigned at runtime allowing to easily customize the calculation procedure. New classes can be defined using object inheritance either in Python or in C++ and used with the existing calculators; as an example, this allows to calculate PDF with a user-defined profile function. A new calculator class can be also defined for any quantity that is obtained by iteration over atom pairs, by defining only the function that processes atom-pair contributions.

For more information about the diffpy.srreal library, please consult our online documentation.

Citation

If you use diffpy.srreal in a scientific publication, we would like you to cite this package as

diffpy.srreal Package, https://github.com/diffpy/diffpy.srreal

Installation

The preferred method is to use Miniconda Python and install from the “conda-forge” channel of Conda packages.

To add “conda-forge” to the conda channels, run the following in a terminal.

conda config --add channels conda-forge

We want to install our packages in a suitable conda environment. The following creates and activates a new environment named diffpy.srreal_env

conda create -n diffpy.srreal_env diffpy.srreal
conda activate diffpy.srreal_env

To confirm that the installation was successful, type

python -c "import diffpy.srreal; print(diffpy.srreal.__version__)"

The output should print the latest version displayed on the badges above.

If the above does not work, you can use pip to download and install the latest release from Python Package Index. To install using pip into your diffpy.srreal_env environment, type

pip install diffpy.srreal

If you prefer to install from sources, after installing the dependencies, obtain the source archive from GitHub. Once installed, cd into your diffpy.srreal directory and run the following

pip install .

Getting Started

You may consult our online documentation for tutorials and API references.

Support and Contribute

Diffpy user group is the discussion forum for general questions and discussions about the use of diffpy.srreal. Please join the diffpy.srreal users community by joining the Google group. The diffpy.srreal project welcomes your expertise and enthusiasm!

If you see a bug or want to request a feature, please report it as an issue and/or submit a fix as a PR. You can also post it to the Diffpy user group.

Feel free to fork the project and contribute. To install diffpy.srreal in a development mode, with its sources being directly used by Python rather than copied to a package directory, use the following in the root directory

pip install -e .

To ensure code quality and to prevent accidental commits into the default branch, please set up the use of our pre-commit hooks.

1. Install pre-commit in your working environment by running conda install pre-commit.

2. Initialize pre-commit (one time only) pre-commit install.

Thereafter your code will be linted by black and isort and checked against flake8 before you can commit. If it fails by black or isort, just rerun and it should pass (black and isort will modify the files so should pass after they are modified). If the flake8 test fails please see the error messages and fix them manually before trying to commit again.

Improvements and fixes are always appreciated.

Before contributing, please read our Code of Conduct.

Contact

For more information on diffpy.srreal please visit the project web-page or email Simon Billinge at [e-mail].

Acknowledgements

diffpy.srreal is built and maintained with scikit-package.