Electronic and structural properties of small clusters ofNanAuandNanAg(n=1–10)

Abstract

Equilibrium geometric structures of ${\mathrm{Na}}_{n}\mathrm{Au}$ and ${\mathrm{Na}}_{n}\mathrm{Ag}$ $(nl~10)$ clusters are obtained by a pseudopotential approach within spin-polarized density-functional theory using the Becke-Perdew-Wang 1991 (BPW91) generalized gradient approximation for the exchange-correlation energy functional. The stability of these clusters is examined via the the analysis of the binding energy (BE) and second difference of energy. Properties related to the electronic structure such as the vertical ionization potential, electron affinity, energy gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, and the hardness are also determined. The BE is largest for the dimer in the ${\mathrm{Na}}_{n}\mathrm{Au}$ series and also has peaks for ${\mathrm{Na}}_{7}\mathrm{Au}$ and ${\mathrm{Na}}_{9}\mathrm{Au}.$ The NaAg dimer, ${\mathrm{Na}}_{7}\mathrm{Ag},$ and ${\mathrm{Na}}_{9}\mathrm{Ag}$ are also found to be more stable in the ${\mathrm{Na}}_{n}\mathrm{Ag}$ series. The vertical ionization potentials of ${\mathrm{Na}}_{n}\mathrm{Au}$ clusters are in good agreement with the available experimental data. The electronic structure of ${\mathrm{Na}}_{n}\mathrm{Au}$ clusters for $n=1,$ 7, and 9 shows that electronic shell closures are responsible for the high stability of these clusters.