Abstract
We study the electronic coupling between two silver nanoparticles using ab initio density functional
theory for real atoms. We show that the electronic coupling depends on both the gap size of the
dimer system and the relative orientation of the particles. As the two particles are separated from
touching contact, the dimer undergoes a bond-breaking step, which also establishes the striking
existence of an optimal gap size de ned by a maximal static polarizability of the dimer. For some
dimers, the electronic coupling before the bond breaking can be strong enough to give rise to a net
magnetic moment of the dimer, even though the isolated particles are nonmagnetic. These ndings
may prove to be instrumental in understanding and controlling the optical, magnetic, electrical, and
chemical properties of closely-packed nanoparticle aggregates.