Designing Coulombic Contact Interactions between Polarizable Particles through Asymmetry

Polarizable particle systems, including charged colloids, polarizable ions, biomolecular assemblies, and soft nanomaterials, can exhibit contact electrostatic interactions that depart strongly from Coulomb behavior when the dielectric mismatch and geometric singularities amplify polarization effects. Here, we use charged dielectric spheres as a model system and show that these polarization contributions can be canceled by jointly tuning size, charge, and dielectric asymmetries. By extending a recently developed image-charge formula to contacting dielectric spheres, at the two-body level, we derive analytical conditions under which the two-body contact interaction reduces to the bare Coulomb form. At the selected design points, accurate two-sphere calculations give root-mean-square (RMS) contact force deviations below 3% from the Coulomb target. Separately, many-body molecular dynamics simulations that retain nonadditive polarization show that under the tested assembly conditions, the structural correlations of six systems satisfying these two-body rules closely match those of their pure Coulomb references. These results establish asymmetry as a route for turning electrostatic complexity into Coulombic simplicity at contact, with implications for predictable and controlled self-assembly and material design.