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

The neutral PrSin (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 PrSin evaluated to be prolate clusters. Starting from n = 20, the ground-state structures of PrSin 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 PrSin 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 PrSin (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.