We are delighted to announce the release of Py-ChemShell 2025 (v25.0), the latest release of the Python-based version of ChemShell.

Highlights of the 2025 release include efficient microiterative optimisation for large QM/MM systems, a new guided workflow for cluster cutting, a new interface to Psi4, improved interfaces to ORCA, Gaussian and PySCF, and significant performance improvements on HPC platforms.

Py-ChemShell 2025 is suitable for production calculations on all types of systems including materials and biomolecules, and we recommend that new ChemShell users use the Python-based version. We also encourage experienced users of the original Tcl-based version of ChemShell to try the Python version and send us your feedback.

The Python-based version of ChemShell is open source software and can be downloaded free of charge from this site. If you have any questions about the code, please get in touch via the community forum.