Designing Coulombic Contact Interactions between Polarizable Particles through Asymmetry

TL;DR

This paper demonstrates how asymmetry in size, charge, and dielectric properties of polarizable particles can be tuned to recover pure Coulombic contact interactions, simplifying complex electrostatic behaviors.

Contribution

It provides analytical conditions and validation methods for canceling polarization effects, enabling Coulomb-like contact interactions in dielectric sphere systems.

Findings

Polarization effects can be canceled by tuning asymmetries.

Derived analytical conditions for Coulomb contact interactions.

Simulations show self-assembly into Coulomb-like structures.

Abstract

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 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, we derive analytical conditions under which the contact interaction reduces to the bare Coulomb form. Accurate two-sphere calculations validate the resulting contact design rules with relative errors below $3\%$. Strikingly, many-body molecular dynamics simulations reveal that systems satisfying these two-body rules self-assemble into structures that closely match their pure Coulomb references. These results establish asymmetry as a route for turning electrostatic complexity into Coulombic simplicity at contact, with implications for controlled self-assembly and materials design.