A DFT study on the structures and stabilities of As-doped Sin−1 (n = 2–15) clusters

The structures and relative stability of pure Sin and AsSin−1 (n = 2–15) clusters have been investigated at the B3LYP/6-31++G(3d) level of density functional theory. In general, the As doping does not lead to fundamental changes in the geometry of the studied clusters; the effects are localized. Relative stabilities of these clusters have been analyzed based on the variation of their averaged binding energies (Eb), fragmentation energies (Ef), second differences in energy (Δ2E), and the highest occupied and the lowest unoccupied molecular orbital (HOMO–LUMO) gaps (ΔE) with cluster size (n). The calculated values of Ef, Δ2E, and ΔE shed light on the relatively high stability of clusters Si12 and Si14 in addition to the well-known magic numbers Si6 and Si10. According to Eb, Δ2E, and Ef results both Sin and AsSin−1 clusters with n = 6, 10, 12, and 14 exhibit high stability when compared to their neighbors. This has been discussed in terms of their close-packed structures rather than electronic pairing effect. The analysis indicates that ΔE of AsSin−1 clusters are significantly smaller than those of the corresponding Sin clusters, especially for n > 4, which means that the metallic characters of AsSin−1 clusters are enhanced by As doping.