To explore the effect of many-body deformations on the activation of the mechanophore, we include a four-body potential to control the dihedral angles around the spiro atom and one the C atoms in the six-member ring, yellow highlight in Fig. . The equilibrium dihedral angle predicted by ReaxFF is 72. A spring constant of 50 kcal/mol is used and the target angle is varied from 70 to 25 across independent CoGEF simulations. We determine the energy barrier for isomerization as the difference in total energy (not including the biasing potential) between the initial configuration and that under which the opening of the C-O bond is observed. Thermalizations (20 ps NVT) were conducted with the external potential prior to CoGEF runs to "pre-deform" the mechanophore to the desired angle of the external potential and keep the initial state at ~300 K.