The ORCA Python Interface (OPI) is a Python library to create input and parse output of ORCA. It is designed as an open source community effort to make ORCA calculations as accessible as possible and is consistently supported by FACCTs, the co-developers of the ORCA quantum chemistry program package. Note that OPI is first introduced with ORCA 6.1 and is not compatible with earlier versions.

• OPI:

  • Documentation (stable): https://www.faccts.de/docs/opi/1.0/docs
  • Documentation (nightly): https://www.faccts.de/docs/opi/nightly/docs
  • Source code: https://www.github.com/faccts/opi
  • Bug reports: https://www.github.com/faccts/opi/issues
  • PyPI: https://pypi.org/project/orca-pi/

• ORCA:

  • Manual: https://www.faccts.de/docs/orca/6.1/manual/
  • Tutorials: https://www.faccts.de/docs/orca/6.1/tutorials/
  • ORCA Forum: https://orcaforum.kofo.mpg.de/

This package can either be installed directly from PyPI with:

pip install orca-pi

or from GitHub:

git clone https://github.com/faccts/opi.git
cd opi
python3 -m venv .venv
source .venv/bin/activate
python3 -m pip install .

More details about the installation can be found in the documentation.

OPI requires ORCA and for parallel calculations also Open MPI. Details on how to install ORCA can be found its manual or tutorials. See Helpful Links. For most modern operating system Open MPI can usually be installed directly with the systems package manager. Otherwise, a suitable version has be obtained and compiled from their website.

Note that OPI is first introduced with ORCA 6.1 and is not compatible with earlier versions. The minimal supported ORCA version is always stored in ORCA_MINIMAL_VERSION

This package comes with a set of tutorials and automatic API reference. The files can be found in docs/. We also host the documentation for the latest stable release and nightly version online. See Helpful Links.

The documentation can also be built from the docs/ folder:

make html

This requires uv which by default is also installed by the Makefile.

This open source project is released publicly under the following open source license: GPL-3.0. This license governs all public releases of the code and allows anyone to use, modify, and distribute the project freely, in accordance with its terms.

The program, including all contributions, may also be included in our proprietary software products under a commercial license. This enables us to:

• Combine open source and closed source components into a single product,
• Offer the project under alternative licensing terms to customers with specific commercial needs,
• Ensure open source compliance for all public parts, while simplifying license obligations in private or embedded distributions.

Contributions are welcome. See How To Contribute for details.

To maintain this licensing model, all contributors must sign our Contributor License Agreement (CLA). This CLA is an adapted industry-standard CLA (Apache CLA) with minor modifications. By signing the CLA, you

• Retain ownership of your contributions,
• Grant us a non-exclusive license to use, sublicense, relicense and distribute your contributions under both open source and proprietary terms.

• Individual CLA (ICLA) for personal contributions,
• Corporate CLA (CCLA) for contributions made on behalf of an employer (available upon request to [email protected]).

For issues or bug reports please create an issue on GitHub. For commercial inquiries contact us directly at [email protected].