The nitrogen edge-doped effect on the static first hyperpolarizability of the supershort single-walled carbon nanotube

The nitrogen edge-doped effect on the structure, dipole moment, and first hyperpolarizability of the supershort single-walled carbon nanotube (5, 0) has been studied systematically. For the nitrogen edge-doped effect on the structure, the mean diameter on the nitrogen-doped side (Du) decreases as the number of doped-nitrogen (n) increases (4.044 (1) > 3.991 (2) > 3.941 (3) > 3.891 (4) > 3.844 A (5)). Significantly, the nitrogen edge-doped effects on the dipole moment and first hyperpolarizability are revealed for the first time and these new effects are dramatic for the supershort single-walled carbon nanotube (5, 0). Among the β0 values of these seven nitrogen-doped structures, the largest β0 (3155 au) is larger by almost 450 times than the very small β0 (7 au) of undoped structure (D5h). For nitrogen-doped structures, the order of the β0 values is 3155 (1) > 2677 (2A) ≈ 2817 (2B) > 1465 (3A) ≈ 1458 (3B) > 670 (4) > 254 au (5), which shows two interesting relationships between the β0 value and nitrogen-doped number: (1) the smaller the nitrogen-doped number, the larger the β0 value. (2) The structures with the same number of doped-nitrogen have almost the same β0 values (1465 for 3A and 1458 au for 3B). As for the frequency-dependent β (−ω; ω, 0) and β (−2ω; ω, ω), the dependence on the nitrogen-doped number (n) is similar to the case of static β0. For β (−2ω; ω, ω) values at ω = 0.005 au are 3220 (1) > 2720 (2A) ≈ 2862 (2B) > 1480 (3A) ≈ 1477 (3B) > 676 (4) > 256 au (5). In addition, the important monotonic dependences of the β value on the Du and electronic spatial extent 〈R2〉 are also observed. The new knowledge of influence the β value will be beneficial to design high-performance nonlinear optical (NLO) materials. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2009