Two versions of ChemShell are available depending on which scripting language is used to control the code, Python or Tcl. At present we continue to maintain both versions of the software, although the Python-based version will eventually supersede the Tcl-based version.

Obtaining Py-ChemShell

The Python-based version of ChemShell is open source software and available free of charge from this website. The latest beta release (v21.0) is available for download here.

We regard Py-ChemShell 21.0 as suitable for production calculations on materials systems, and would encourage materials modellers to consider switching from Tcl-ChemShell to Py-ChemShell if they haven’t already done so.

Py-ChemShell 21.0 is the first beta release to include support for calculations on biomolecular systems, including a guided protein solvation workflow and automated import of CHARMM and AMBER forcefields for biomolecular QM/MM calculations. We encourage experienced ChemShell users to try the new functionality and send us feedback on your experience. For new users, we would currently still recommend using Tcl-ChemShell for biomolecular calculations until the next beta release of Py-ChemShell, which is anticipated for summer 2022.

Obtaining Tcl-ChemShell

The original Tcl-based version of ChemShell is licenced under a proprietary STFC licence. We are distributing the latest version of the code (v3.7) to academic research groups on receipt of a completed licence agreement and (in the case of non-UK licencees) a licence fee of 500 UK Pounds. The license covers the ChemShell code, not the standalone quantum chemistry or MD codes to which ChemShell provides interfaces.

You can download a copy of the Academic Licence form which should be completed, scanned and emailed to Tom Keal.

To make the licence payment by bank transfer, please see the  ChemShell payment instructions.

To pay by credit card please use the ChemShell licence payment site.

In case of any problems making the payment, please contact Damian Jones.

UK academic groups should use the Royalty Free licence and do not need to make a payment.

Please note that no changes can be made to the academic or royalty free licence terms and conditions.

For commercial licencing of Tcl-ChemShell, or for any further information please contact Tom Keal.