A theory for like-charge attraction of polarizable ions

A theory that explains how like-charge attraction of polarizable ions could occur is presented. Based on an effective-dipole description, the theory predicts that, for a pair of spherical polarizable ions in vacuum, like-charge attraction is possible but opposite-charge repulsion could not occur, where any occurrence of like-charge attraction is necessarily conditional upon dissimilarities in net charge or polarizable volume between the particles. It also predicts a correlation between the nature of interaction and the alignments of effective-dipole moments. The findings, which echo recent theoretical predictions of like-charge attraction for a pair of dielectric spheres in vacuum, suggest that this counterintuitive phenomenon could be realized in systems of different length scales through similar mechanisms of particle dissimilarities.