Structural, electronic, and optical properties of noble metal clusters from first principles

We examine low-energy isomeric forms, static polarizabilities, and optical absorption spectra of Ag-n , n = 2-8, and Au-n , n = 2-3, clusters using first principles computations within the static and time-dependent versions of the density functional theory. The noticeable decrease in the static polarizabilities of Ag-7 and Ag-8 compared to the values characteristic of Ag-n , n = 2-6, is correlated with the transition from two-dimensional to three-dimensional structures at n = 7. The optical spectra computed within the time-dependent local density approximation for the most stable structures are in good agreement with the available experimental data and the results of earlier theoretical studies. Optical spectra of higher-energy isomers typically present features that are not observed in the experimental spectra. The d electrons affect the spectra of noble metal clusters by quenching the oscillator strengths through screening of the s electrons and by getting directly involved in the excitations. Due to the larger s-d hybridization in Au compared to Ag, these effects are more pronounced in Au-n clusters.