Atomistic Electrodynamics Model for Optical Properties of Silver Nanoclusters

In this work we have presented an atomistic electrodynamics model for describing the optical properies of silver clusters in the size range of 1-5 nm. The model consists of interacting atom-type capacitances and polarizabilities that combined describe the total response of the nanoclusters. A double Lorentzian oscillator is used to describe the frequency-dependent atomic polarizabilities, while a single Lorentzian oscillator is used to describe the frequency-dependent atomic capacitances. All atomic parameters have been optimized using reference data obtained from time-dependent density functional theory (TDDFT) calculations. As a comprehensive test of our model, we have studied the frequency-dependent polarizabilities of quasi-spherical silver nanoclusters having different structural motifs, i.e,, icosahedra, truncated Ino and Marks decahedra, and regular truncated octahedra and cubocahedra. We have shown that Clusters in all five structural motifs exhibit a strong absorption peak in the spectral region of 2.4-4.8 eV, although the size evolution of absorption peak location and peak width depends strongly on the number of atoms, and the atomic arrangements of the clusters.