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

The geometrical and electronic properties and growth patterns of the bimetal Pd₂ doped Si_n (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 Pd₂Si_n (n = 10–20) are based on the pentagonal prism PdSi₁₀. The bimetal Pd₂ is doped on the opened cage-like silicon clusters (Si_n) with the range of size n = 10–15, while doped on bigger silicon clusters (Si_n, n = 16–20), the Pd₂ are completely encapsulated inside Si_n frames. The geometrical configurations of the encapsulated Pd₂ in the Si_n frames are varied due to the interactions between Pd₂ and Si_n frames. The calculated fragmentation energies reveal that the remarkable stable Pd₂Si_n 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 Si_n clusters are similar to those of the single TM doped silicon clusters. In addition, the Pd₂Si_n (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. - Highlights: • The remarkable stable Pd₂Si_n with n = 11, 13, 16, 18, 20 is observed. • Critical size of geometry transition is explored at n = 16. • The charges transfer from Pd₂ to Si_n. • Pd₂Si_n (n = 10,13,14,16,17) has enhanced chemical stability