Effect of separation on second-order hyperpolarizability of two silver nanoclusters

We present a study on dielectric response of Ag14 nanocluster dimer using first principles methods. The interaction energy, (hyper)polarizability of dimer are predicted under various separations of the two identical Ag14 nanoclusters. The appropriate separation makes the second-order hyperpolarizability of Ag14 dimer is about 70 times larger than the Ag14 monomer. The increase of polarizability and hyperpolarizability is ascribed to reconfiguration of molecular electronic state from Ag cluster monomer to dimer. Nonlinear response is more susceptible to the steady intermediate state compared to linear response. The crucial transitions contributed to hyperpolarizability are assigned to be from highest occupied molecular orbitals to the lowest unoccupied molecular orbital (HOMOs-LUMO) of nanocluster dimer. Binding character of LUMO plays an important role in determining nonlinear optical properties.

► The reconfiguration contributed to hyperpolarizability.
► The transitions are assigned to be from occupied orbital to LUMO.
► Binding character of LUMO plays an important role.