The Open Force Field Initiative makes a number of resources available to the community, including open source software, high-quality curated open datasets, and force fields.


  • SMIRNOFF white paper: This preprint/white paper introduces the SMIRNOFF format in the context of traditional force fields, explains the development and validation of our new small molecule force field smirnoff99Frosst, and highlights some directions the initiative is headed.


  • openforcefield: A Python toolkit from the Open Force Field Initiative for the development and use of modern molecular mechanics force fields based on direct chemical perception and parameterized with rigorous statistical methods. This also provides the SMIRNOFF force field format.
  • open-forcefield-tools: Development space for property calculation and force field parameterization tools.
  • SMARTY: A simple prototype implementation Bayesian atom type sampling using reversible-jump Markov chain Monte Carlo (RJMCMC) over SMARTS types. This also provides the SMIRKY tool, which samples over SMIRKS patterns for chemical perception of parameter types.



  • smirnoff99Frosst: The first general-purpose implementation of a SMIRKS Native Open Force Field (SMIRNOFF) as implemented by the SMIRNOFF ForceField class (in openforcefield.typing.engines.forcefield) for parameterizing small molecules for OpenMM and (via ParmEd and InterMol) a wide variety of other simulation packages.