Reaction-profile diagrams for all four models are shown in Fig. , with vibrational free energy corrections (-T ∆S vib ) computed at T = 298.15 K. Entropic and ZPE effects both generally stabilize the transition state and the product state relative to the reactant state, and they do so to a much greater degree than the 0. As model size increases from I to III, the fixed-atom models go from having the highest product energy to having the lowest, although results for model IV are sim- ilar in this respect. For the fixed-atom models, difference between transition state and product energies become more pronounced in models II and III as compared to model I but then contract significantly in model IV. In all cases the difference between transition state and products is smaller when harmonic confining potentials were used. This suggests that the harmonic restraints ef-fectively mitigate rigidity, and imparting physical meaning to the anchor atoms, particularly when dealing with smaller models.