NPs, which indeed led to the formation of a 2D hexagonal sheet (Fig. ). Interestingly, 𝑊 ! * ≈ -30 𝑘 * 𝑇 for contacting pairs of NPs (Fig. ) and ∆𝑊 % * ≈ 10 𝑘 * 𝑇 for contacting triangles of NPs (Fig. ), so the three-body repulsion is smaller than -𝑊 ! * /2 required to promote formation of 2D sheets, as per our earlier discussion (Fig. ). This is because NPs in macroscopic 2D hexagonal sheets possess more triads of NPs compared to the 4-NP sheet, as schematically shown in Fig. . Since the net repulsion that a NP experiences is given by the sum of the three-body repulsions arising from all triads that the NP forms with neighboring NPs, a smaller strength of repulsion per triad is sufficient to promote the formation of 2D sheets.