= Solution
For $\alpha>0$, the given model predicts \b[attraction proportional to $r^{-5}$ in <force>], independent of the ion's charge sign; the <energy> is proportional to $-r^{-4}$ and vanishes at large separation. A larger <electric polarizability> gives a stronger interaction.
This is induction by a charged object. Ordinary nonretarded London interaction between two small neutral polarizable objects instead has an $R^{-6}$ <energy> dependence; geometry-integrated colloidal dispersion laws can have other powers. Calling the specified $r^{-4}$ law a generic dispersion <force> would conceal its charge-dependent origin.
Attraction can favor association or adsorption. A stable suspension normally requires an opposing free-energy barrier, such as double-layer or <steric repulsion>, relative to <Brownian motion>. Salt, surface coatings and solvent quality alter that balance. However, one ion–particle pair potential alone does not establish the phase behavior or aggregation rate of a many-particle suspension; concentrations, diffusion, surface chemistry and the remaining interactions also matter.
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