Probing the structural and electronic properties of bimetallic Group-III metal-doped gold clusters: AunM2 (M = Na, Mg, Al; n = 1–8)

Abstract

Employing first-principles density functional theory at the PW91PW91 level, the equilibrium geometries, relative stabilities, and electronic properties of bimetallic Au n M2 (M = Na, Mg, Al; n = 1–8) clusters have been systematically investigated in comparison with pure gold clusters. The optimised results indicate that the doping atom Na trends to occupy a peripheral site in the host, while Mg and Al atoms favour the center site. Furthermore, Al-induced geometries become three-dimensional more easily. Much to our surprise, in the most stable isomers, doping with binary Group-III metal atoms markedly changes the geometries of the ground-state Aun+2 clusters, and higher average atomic binding energies are found in Al-doped clusters. The calculated fragmentation energies, second-order difference of energies, HOMO-LUMO energy gaps, and chemical hardness as a function of cluster size exhibit a pronounced odd-even alternating phenomenon, suggesting the clusters with closed electronic shells have higher relative stabilities. A natural population analysis has been performed to understand the effects of different doping atoms on electronic properties.