Following the methods used to parametrize the base OpenFF, at each grid point, the four atoms forming the targeted dihedral are held fixed, and all remaining atoms undergo a MM relaxation with a harmonic energy restraint of 1 kcal/mol/ Å 2 . This ensures that the overall conformation of the molecule remains close to the QM minimum, while ensuring that the torsion parameters do not have to compensate for deficiencies in the other terms in the force field, such as overly stiff repulsive LJ interactions with nearby atoms in the molecule.