Effect of mono- and multivalent salts on angle-dependent attractions between charged rods

The effective interactions between two like-charged rods were examined as a function of angle and separation using molecular dynamics simulations. The effect of concentrations of simple and multivalent salts on the electrostatic repulsions and multivalent-ion-induced attractions were determined. It was found that the stable configuration of two rods evolves from isolated rods to aggregated perpendicular rods to aggregated parallel rods as a result of an increase in the multivalent salt. Monovalent salt was found to enhance the attraction near the onset of aggregation, and reduce it at a higher concentration.