Structures, Stabilities, and Electronic Properties of Gold Silicide Clusters: Comparison with Pure Silicon Clusters

The local meta-GGA (generalized gradient approximation) exchange correlation density functional (TPSS) with relativistic effective core potential was employed to systematically investigate the geometric structures, stabilities, and electronic properties of bimetallic Au2Sin (n = 1 – 8) clusters. The optimized geometries show that the most stable isomers have a three-dimensional structure except for Au2Si1,3 clusters. The doped gold atoms prefer to occupy the surface site in the Au2Sin clusters. Here, the averaged atomic binding energies and fragmentation energies show that the Au2Si5 isomer is the most stable among the Au2Sin (n = 1 – 8) clusters. A pronounced even-odd alternation is found in the energy difference between the highest occupied and the lowest unoccupied molecular orbital (HOMO–LUMO gaps), especially, the Au2Si5 cluster has the largest HOMO–LUMO gap of 2.06 eV. Moreover, the reverse even–odd alternation rule to the average polarizability per atom versus the charges transfer was found. A transition point appears at n = 5.