To investigate how different ligands affect the interparticle interactions of NCs in solution, we calculated the potential of mean force (PMF) between a pair of NCs. Figure shows the PMF of PbSe NCs capped with OD ligands, showing a characteristic double-well profile, similar to gold nanoparticles adsorbed with octadecanethiol. Specifically, at longer interparticle distances, the potential well reaches a depth of ε t = -26.5 kJ/mol, corresponding to the "touch" mode of NC contact (Figure ). The negative sign indicates that the interaction is attractive compared to the separated, non-interacting NCs. At shorter distances, the well deepens further to ε l = -74.5 kJ/mol, representing the "lock" mode contact. For ligands modified at the proximal or middle positions, the PMF between NCs is purely repulsive (Figures ), which aligns with the lower degree of ligand bundle ordering observed for these configurations (Figure ). For instance, mDB ligands typically represent the ligands commonly used in experiments, such as oleic acid or oleylamine, while BC-modified ligands, with their branched chains, act as entropic ligands that enhance NC solubility and colloidal stability. As is shown in Figures , when the modification occurs at the distal position, ligandligand interactions introduce a degree of attraction, and both touch and lock contact modes are observed for all ligands with distal modification. For NCs capped with d-DB ligands, the attractive strength is significantly reduced compared to that of OD (Figure ). In this system, the potential well depth in the touch mode (ε t ) is -22.0 kJ/mol, while in the lock mode (ε l ) it is -34.8 kJ/mol. We attribute this decrease in attraction to the lower crystallinity of ligands induced by the terminal DB group. In the dBC ligand system (Figure ), the interparticle attraction diminishes further, with ε t reduced to -14.1 kJ/mol, and the PMF of the lock mode becomes positive, indicating a metastable rather than a stable state.