Extended Hückel tight-binding calculations of electronic resonances in linear chains of gold atoms and clusters

Electronic excitations in linear chains and icosahedra clusters of gold atoms have been studied using an approximate version of time-dependent density functional theory based on the extended Hückel tight-binding method. The formation and development of two longitudinal collective resonances in the absorption spectra were studied as a function of the chain length. We show that in the case of a gold cluster dimer, the classical description breaks down at intercluster distances below 0.5 nm due to the neglect of important quantum effects. In addition, a blue shifting of the collective resonances at these distances is observed. Analysis of these results yields a general picture of electronic resonances in one-dimensional atomic structures.