Abstract:
Using C
32 molecule as the skeleton of multipole moments, two types of substitutional co-doped fullerene derivatives C
28B
2N
2 and C
28B
2P
2 were designed with 16 isomers. The electronic properties, linear polarizability
α and first hyperpolarizability
β were studied by CAM-B3LYP method of density functional theory (DFT). The results show that the HOMO-LUMO gap of the doped molecules becomes smaller, and the values of
α and
β of C
28B
2P
2 are larger than those of C
28B
2P
2. Additionally, dipole molecules in these molecules have large
β, while the octapolar molecules have smaller
β. The structure with excellent second-order nonlinear optical (NLO) response characteristics is selected. The calculation results of time-dependent density functional theory (TD-DFT) method show that, compared with C
32, the response range of absorption spectra of all doped structures becomes wider, the maximum intensity becomes weaker, and the position of the maximum absorption wavelength may be red-shifted or blue-shifted. Based on the sum-over-states (SOS) method, the two-level or three-level formulas are used to explain the origin of large
β in two co-doped structures, and verify the related electronic excitation type is π→π* excitation.