A tight-binding model for the optical properties of Au55-clusters

Abstract

Abstract.We have computed the electronic structure and the imaginary part of the dielectric function of the Au55 cluster using a tight-binding model which takes into account size and boundary effects. Besides the Drude behavior, we obtain anomalous absorption peaks in the infrared region due to the breakdown of the selection rule Ak=O. Taking into account surface coating effects, the onset of the interband absorption above 2.5 eV results to be red shifted, in agreement with the experimental data. As a consequence, we obtain a dramatic increase of the width of the plasmonic absorption peak, which accounts for the experimental optical spectra observed by Kreibig. PACS: 36.40. + d; 78.40.

Ab initio calculations of optical properties of silver clusters: cross-over from molecular to nanoscale behavior

“…Full quantum investigations are often limited to few atoms clusters. These involve tight-binding calculations [20][21][22], and the time-dependent density functional theory (TDDFT) approach [22]. A promising atomistic method that can be conveniently used on hundreds of atom systems is the capacitance-polarizability interaction model [23,24] which has been successfully used to study the effect of planar defects on the optical properties of Ag nanostructures [25].…”

Third-order optical susceptibility of small metallic particles

“…3 the interband contribution is reported for two different values of the surface parameter Z; for a negative value, due to the interaction with a reducing medium, the absorption threshold is red-shifted. This phenomenon is also responsible for the anomalous width and shift of the surface plasma resonance in extremely small gold particles [8].…”

“…In order to take into account the shallow-lying d-band, we have recently proposed a tight-binding model for the calculation of the dielectric function and of optical absorption [8,9]; this approach allows a proper interpretation of the size-dependent plasma resonance when the surface states and interaction with the matrix are considered. In this paper we extend our model to the non-linear susceptibility and investigate the role of surface and size effects on the non-linear optical properties of these composite materials.…”

“…Analogous results hold for thirdharmonic generation and the Kerr effect. The tight-binding model for a cluster in the separate band approximation is fully described in [8,9]. We expand the solutions of the Schr5dinger equation in a local function set, defined by the orbital quantum numbers 1 and m of the atomic states:…”

“…The electronic structure of the cluster turns out to depend both on size and surface effects -DOS of a cuboctahedral particle of 55 atoms of gold. The tight-binding parameters we used are reported in [8]. The electronic structure, which is intrinsically discrete, has been smeared out by the convolution with a Gaussian function.…”