Stability and electronic properties of praseodymium-doped silicon clusters PrSin (n = 12-21)

The neutral PrSi _n (n = 12-21) species considering various spin configurations were systematically studied using PBE0 and B3LYP schemes in combination with relativistic small-core potentials (ECP28MWB) for Pr atoms and cc-pVTZ basis set for Si atoms. The total energy, growth-pattern, equilibrium geometry, relative stability, hardness, charge transfer, and magnetic moments are calculated and discussed. The results reveal that when n < 20, the ground-state structure of PrSi _n evaluated to be prolate clusters. Starting from n = 20, the ground-state structures of PrSi _n are evaluated to be endohedral cagelike clusters. Although the relative stabilities based on various binding energies and different functional is different from each other, the consensus is that the PrSi₁₃, PrSi₁₆, PrSi₁₈, and PrSi₂₀ are more stable than the others, especially the PrSi₂₀. Analyses of hardness show that introducing Pr into Si _n (n = 12-21) elevates the photochemical sensitivity, especially for PrSi₂₀. Calculated result of magnetic moment and charge transfer shows that the 4f electrons of Pr in the clusters are changed, especially in endohedral structures such as PrSi₂₀, in which one electron transfers from 4f to 5d orbital. That is, the 4f electron of Pr in the clusters participates in bonding. The way to participate in bonding is that a 4f electron transfers to 5d orbital. Although the 4f electron of Pr atom participates in bonding, the total magnetic moment of PrSi _n is equal to that of isolated Pr atom. The charge always transfers from Pr atom to Si _n cluster for the ground state structures of PrSi_n (n = 12-19), but charge transfer is reverse for n ≥ 20. The largest charge transfer for endohedral structure reveals that the bonding between Pr and Si _n is ionic in nature and very strong. The fullerenelike structure of PrSi₂₀ is the most stable among all of these clusters and can act as the building blocks for novel functional nanotubes.