The present Parsley force field, formally named openff-1.0.0, can be accessed from Python by installing the Open Force Field Toolkit with the command conda install -c omnia openforcefield openforcefields and then loading the force field as follows: from openforcefie ld . typing . engines . smirnoff import ForceField ff = ForceField ( ' openff -1 . 0 . 0 . offxml ')