Smirnoff-plugins is an open source and highly flexible framework to extend SMIRNOFF-style force fields with custom interaction potentials. The energy expression is implemented in a non-bonded interaction class, and the package automatically handles scaled 1-4 non-bonded interactions via a custom bond force and has support for virtual sites. Currently smirnoff-plugins offers implementations of the damped Buckingham-6-8 and double exponential potentials used in this work, but others may be trivially added. The package makes use of the openff-toolkits plugin framework which is able to use custom potential definitions to load parts of SMIRNOFF force fields that it does not recognise. In this case, the DE potential and its associated parameters would be loaded and applied to an OpenMM system by smirnoff-plugins, with all other standard terms (electrostatic and valence) handled by the openff-toolkit. Thus, once the package is installed, users are able to use these custom potential force fields with very minor code changes to their current workflows, for example the following code could be used to load such a force field with the openfftoolkit 37 : from openff.toolkit import ForceField ff = ForceField( "de-force-1.0.0.offxml", load_plugins=True )