Density Functional theory investigations on the geometrical and electronic properties and growth patterns of Sin (n = 10-20) clusters with bimetal Pd2 impurities

The geometrical and electronic properties and growth patterns of the bimetal Pd2 doped Sin (n = 10-20) clusters have been studied systematically by density functional theory. The growth-pattern behaviors, relative stabilities, and chemical bonding of these clusters are presented and discussed. The optimized geometries exhibit that the dominant growth patterns of Pd2Sin (n = 10-20) are based on the pentagonal prism PdSi10. The bimetal Pd2 is doped on the opened cage-like silicon clusters (Sin) with the range of size n = 10-15, while doped on bigger silicon clusters (Sin, n = 16-20), the Pd2 are completely encapsulated inside Sin frames. The geometrical configurations of the encapsulated Pd2 in the Sin frames are varied due to the interactions between Pd2 and Sin frames. The calculated fragmentation energies reveal that the remarkable stable Pd2Sin clusters with n = 11, 13, 16, 18, and 20 are observed. Among all different-size clusters, the Pd2-doped Si16 is the most stable cluster. Particularly, the cage-like Pd2Si16 geometry is obviously distinct as compared to the single transition metal doped silicon cluster. Interestingly, the critical size of geometry transition is explored at n = 16. Natural population analysis manifests that the charge-transfer phenomena in the Pd2-doped Sin clusters are similar to those of the single TM doped silicon clusters. In addition, the Pd2Sin (n = 10, 13, 14, 16, and 17) isomers have enhanced chemical stabilities because of their larger gaps between the highest occupied orbital and the lowest unoccupied orbital.