Absorption spectra and electronic structures of Au mAg n ( m + n = 8) clusters

The electronic structures and absorption spectra of Au _mAg _n ( m + n = 8) clusters have been investigated using time-dependent density functional response theory. We have discovered that the vertical ionization potentials, highest occupied molecular orbital level, lowest unoccupied molecular orbital level and binding energies of the most stable binary Au _mAg _n are intermediate between those of Ag ₈ and Au ₈ clusters. The analysis of the low-energy absorption spectra shows that the dominant excitation energies and the corresponding oscillator strengths exhibit an obvious odd-even oscillation with the variation of the number of Au atoms. The odd-even oscillation character indicates that the optical properties of Au _mAg _n can be tuned by changing the stoichiometries. The excitation of electrons to exterior atoms plays a key role in optical responses of Au _mAg _n clusters.