Investigation of curvature effects on the nitrogen and boron electric field gradient and chemical shielding tensors in the mono-BN-substituted fullerenes: A density functional theory

The density functional theory is used to investigate the effects of local structures and curvature on the nitrogen and boron electric field gradients and chemical shielding tensors in the Cn−2BN heterofullerenes (n=20, 24, 28, 32, 36, 50, 60, and 70). Geometry structures of all the mono-BN-substituted fullerenes have been fully optimized at the B3LYP/6-31G⁎ level of theory. The spherical excesses φi are used to characterize the curvature of fullerene at the boron and nitrogen sites. The φi at the N sites in the mono-BN-substituted fullerenes significantly increases in comparison to the standard value of φi at the corresponding site in the perfect fullerene cages, indicating that the N atom relaxes outside the surface of the cage. In contrast to 15N CSA, an increasing trend is observed for 15N CSI and 14N CQ of the sites with the increase of curvature. Comparing the results for curved and relaxed fragments with those in the heterofullerene cages suggests high sensitivity of CS and EFG parameters to the curvature of fullerene structure.