First-principles study of torsional single-walled carbon nanotubes

Abstract

The controllable band gap of single-walled carbon nanotubes (SWCNTs) has been a prominent area of research. This study introduces a torsional model that involves rotating each carbon atom along the axial direction of SWCNTs, accompanied by a detailed description of the model creation process. Two guidelines for constructing the model are proposed, and the self-consistency of the torsion model is established through first-principles density functional theory. Initially, the band gap map of SWCNTs under torsion is presented. As the twist strength increases, the band gap of SWCNTs undergoes several phase transitions, including semiconductor-metal and metal-semiconductor transitions. Moreover, we investigate the variations in the average bond length, average bond angle, and diameter of SWCNTs under torsion. Furthermore, this study delves into the analysis of carbon atomic energy statistics, revealing distinct energy changes for different types of single-walled carbon nanotubes under identical torsion intensities. The findings shed light on the controllable band gap of SWCNTs, offering a theoretical foundation for the development of nanoelectronic devices and microintegrated circuits utilizing single-walled carbon nanotubes. In conclusion, this research presents a novel approach for exploring the controllable band gap of single-walled carbon nanotubes through torsional manipulation. Theoretical insights into the behavior of SWCNTs under torsion provide valuable contributions to the field and pave the way for potential applications in nanoelectronics and microintegrated circuits.

Estimation of the Band Gap of Carbon Nanotube Bundles

“…ZSWCNT represents the length of the supercell along the Z-axis, as shown in Figure 13b. Atom i underwent a central rotation of Figure 15 shows the effect of torsion on the SWCNTs' band gap [40]. The band gaps of armchair tubes showed quite large fluctuations (metal→semiconductor→metal) with a rough period 0.8 rad/nm when the torsional strength increased from 0 rad/nm to 1.2 rad/nm.…”