Understanding the stabilities and non-linear optical response of transition metal endo-doped B₁₂N₁₂ and B₁₂P₁₂ nanocages; a density functional theory investigation

Abstract

Electronic and nonlinear optical properties of endohedral 3d transition metals (TMs) doped on B12N12 and B12P12 nanocages (TM@X12Y12) are studied. The spin-polarized calculations are carried out considering the four lowest possible spins in all TM@X12Y12 complexes. For understanding the interaction between transition metals and nanocages, Zero-point energies (ZPE) and Gibbs free energies of adsorption are considered. The results of Zero-point energies and Gibbs free energies reveal that transition metals (TMs) are chemisorbed with exothermic interaction energies in B12P12 nanocage. Natural Bond orbital (NBO) analysis reveals that the TM@B12N12 are true metallides, especially for Ti, V, and Cr with the negative values of NBO charges on metals whereas TM@B12P12 possesses electride characters. Dipole moments analysis reveals that metals placed in the center do not cause significant changes in the dipole moment. Bond order analysis gives the higher bond order values for early transition metals in B12N12 and B12P12 complexes. However, bond order tends to decrease in late transition metals for both nanocages. Frontier molecular orbital (FMO) analysis is performed to understand the effect of TMs on the electronic properties of B12N12 and B12P12 nanocages. By applying a long-range separated method, polarizability and hyperpolarizability values are calculated. The enhanced non-linear optical (NLO) response is observed for early transition metals in B12N12 nanocage. Whereas late transition metals showed a higher response for B12P12 nanocages. The values obtained of α and β o for TM@B12N12 are in the range of 166-218 and 42-2695 au. Whereas the values of α and β o for TM@B12P12 are in the range of 408-457 and 1-5122 au. These results prove that these nanocages are potentially effective for high-performance non-linear optical devices.