The optimized values of these fit parameters along with the forms of the symmetrized terms are listed in Table . The RMSD over the full training set is 1.241 𝑘 * 𝑇, and the RMSD over data in the lowest 5 𝑘 * 𝑇 energy range is 0.673 𝑘 * 𝑇 (Fig. ). Figure presents a contour map of the fitted PIP along 𝑑 4% and 𝑑 !% , for fixed 𝑑 4! = 6.12𝜎, corresponding to the case where a pre-assembled dimer of contacting NPs is approached by a third NP. The fitted PIP shows excellent agreement with the MD-computed free energies (white circles).