A reasonable criterion of nitrogen-doped single-walled carbon nanotubes with pyridine-like configurations

Bond curvature KD as a universal criterion is used to identify structures and reactivities of N2-doped single-walled carbon nanotubes. Calculations of adjacent N2-dopings show that, as KD is large, a pyridine-like structure is formed and the formation energies Ef linearly decrease with increasing KD, whereas as KD is small, the doping N–N bond cannot be broken. A boundary of KD between generating broken and unbroken N–N bond structures is about 1.6 nm− 1. For the (n,0) tubes, the Ef of products with the pyridine-like configurations have an odd–even oscillation rule with n values, and display a decreasing trend with increasing KD. As the largest value Klargest among all KD in a given tube is small, two N atoms are inclined to disperse in the tube and its product has a perfect sp2 hexagonal network configuration. The approximate border value of Klargest for the adjacent and disperse substitutions is 2.3 nm− 1.