Open Force Field Software

The Open Force Field Initiative is creating molecular mechanics force fields for simulation of large biomolecular systems, and the tools to use them easily and accurately. OpenFF force fields are optimized automatically and in the open, with open source tools, from open source datasets. We assign parameters directly to chemical graphs without the intermediate step of assigning atom types, and we can export parametrized systems to a host of simulation engines.

Getting Started

Instructions for installing and using OpenFF software can be found at Installation and in the project-specific documentation below. If you want to understand how to use OpenFF force fields, or if you want to see what’s possible, see Modelling with OpenFF or the Examples.


Specifications for SMIRNOFF and other standards defined by OpenFF can be found at OpenFF Standards.



Tools for preparing systems and manipulating force fields


Parametrize and export systems ready for simulation to various MD engines


Unified units of measure handling for the OpenFF ecosystem based on Pint


Automated parameter optimization for specific molecules or series of molecules


Submit and retrieve datasets with rich metadata from QCFractal instances


Fragment molecules for efficient quantum mechanical torsion scans


Scalably and automatically estimate physical properties


Generate optimized partial charges for molecules with a variety of methods


Train and use machine-learned partial charge models targetting molecular graphs

Contact Us

Need help? Raise an issue on GitHub, open a discussion on OpenFF Discussions, or email us!