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 (v23.0) is available for download here.

We consider Py-ChemShell 23.0 to be suitable for production calculations on both materials systems and biomolecules, and recommend that new ChemShell users should use the Python-based version.

Support for calculations on biomolecular systems in Py-ChemShell has been present since v21.0, including a guided protein solvation workflow and automated import of CHARMM and AMBER forcefields for biomolecular QM/MM calculations. New features in v23.0 include support for CHARMM-style residue patching and an interface to TURBOMOLE. We encourage experienced ChemShell users, especially those who use TURBOMOLE as their preferred QM package, to try the biomolecular modelling functionality in Py-ChemShell and send us feedback on your experience.

Obtaining Tcl-ChemShell

We continue to maintain the original Tcl-based version of ChemShell and distribute it on request. Tcl-ChemShell currently contains some features that are not yet available in Py-ChemShell (but will be soon!) including a QM/MM MD driver and multiple electronic state calculations. At the present time if you need this functionality you will need to obtain a licence for Tcl-Chemshell.

Tcl-ChemShell is licenced under a proprietary STFC licence. We distribute 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. Note that the license covers the ChemShell code, not the standalone quantum chemistry or MD codes to which ChemShell provides interfaces, which must be obtained separately.

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.