Geometries, stabilities, and electronic properties of Y-doped Sin (n = 1-16) clusters: A relativistic density functional investigation

The geometries, stabilities, and electronic properties of Y-doped Sin (n = 1-16) clusters are investigated systematically via a relativistic density functional theory with the generalized gradient approximation. For n = 1-14, the most stable YSin geometries generally keep the analogous frameworks to the low-lying Sin+1 clusters, and especially in the size range n = 11-14, they are prolate in shape and form sandwich structures with Y atom occupying a surface site. When the cluster size goes up to 15, the Y atom abruptly drops into the silicon cage, together with the alteration in the direction of charge transfer revealed by the Hirshfeld charge analysis. The calculated atomic averaged binding energies and fragmentation energies manifest that the YSin (n = 2, 5, 8, 11, and 14) clusters have remarkably enhanced stabilities. Moreover, the gaps between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of YSin clusters are universally narrow, compared with those of pure silicon clusters. The calculated HOMO and LUMO energies for Y-encapsulated YSin (n = 15, 16) are evidently lower than those of the small-sized YSin (n = 1-14) clusters.