Structure of chiral single-walled carbon nanotubes under hydrostatic pressure

TL;DR

This study analyzes how the structure of chiral single-walled carbon nanotubes changes under hydrostatic pressure, revealing bond length compression, shape transitions, and the influence of chirality and radius.

Contribution

It provides a detailed analysis of structural parameters of chiral nanotubes under pressure using symmetry-based methods and Tersoff potential, highlighting unique behaviors compared to achiral tubes.

Findings

Bond length decreases with pressure

Cross-sectional shape transitions from circular to oval

Bond length at transition is identical across chiral tubes

Abstract

We investigate the structural parameters, i.e. bond lengths and bond angles of chiral tubes of various chiralities. The procedure used is based on helical and rotational symmetries and Tersoff potential. The results indicate that at ambient condition, there are equal bond lengths and three unequal bond angles in the structure of chiral tubes. The bond length depends much more on the chirality and very slightly on the tube radius. Length of the tubes does not play very significant role on bond length and bond angles. These C-C bonds were recalculated under hydrostatic pressure. The bond length compresses with pressure while the bond angles remain practically unchanged. We also carry out analysis regarding the cross sectional shape of chiral tubes and its pressure dependence. It is found that at some pressures, transition from circular to oval cross section takes place. The transition pressure is found to strongly depend on the radius and chirality of tube. At this transition, corresponding to given elliptical cross section, the bond length for all chiral tubes is identical. This behavior of bond length is different from achiral tubes.