Helical Carbon Segment in Carbon–Boron–Nitride Heteronanotubes: Structure and Nonlinear Optical Properties

Carbon–boron–nitride heteronanotubes have attracted much interest owing to their adjustable properties and wide applications in many fields. In this work, the structures and first hyperpolarizabilities ( β 0 ) of a series of HA‐ n and isoelectronic PA‐ n heteronanotubes are investigated, in which HA‐ n is composed of a helical C segment and BN segment, and PA‐ n is composed of an arc C segment and BN segment. Interestingly, the helix C segment in HA‐9 leads to a fascinating long‐range charge‐transfer character. As a result, the β 0 value of HA‐9 is 1.80×10 4  a.u., which is much larger than that of PA‐9 (4.99×10 3  a.u.). Significantly, the β 0 value of the C segment in HA‐9 is 1.72×10 4  a.u., whereas that of the BN segment in HA‐9 is much smaller (7.48×10 2  a.u.). In this context, the larger β 0 value of HA‐9 is essentially induced by the helix topological effect of the C segment. It is our expectation that this new knowledge about heteronanotubes might provide more ideas for further exploration of sp 2 ‐hybridized carbon segments with special topologies.