Pressure effects on bond lengths and shape of zigzag single-walled carbon nanotubes

TL;DR

This study examines how pressure influences bond lengths and cross-sectional shape in zigzag single-walled carbon nanotubes, revealing unique behaviors compared to armchair and chiral tubes through theoretical modeling.

Contribution

It provides detailed insights into pressure-induced structural changes in zigzag nanotubes using a symmetry-based theoretical approach and Tersoff potential calculations.

Findings

One bond length equals graphite's bond length; the other is larger.

Under pressure, only the larger bond length compresses.

Transition from circular to oval cross section occurs at 2.06 GPa.

Abstract

We investigate structural parameters, i.e., bond lengths and bond angles of isolated uncapped zigzag single-wall nanotubes in detail. The bond lengths and bond angles are determined for several radii tubes by using a theoretical procedure based on the helical and rotational symmetry for atom coordinates generation, coupled with Tersoff potential for interaction energy calculations. Results show that the structure of zigzag tubes is governed by two bond lengths. One bond length is found to have a value equal to that of graphite, while the other one is larger. Furthermore, the tube length is found to have significant effect only on larger bond length in zigzag tubes. With the application of the pressure, only the larger bond length compresses, the other one remaining practically constant. At some critical pressure, this bond length becomes equal to constant bond length. This behavior of bond lengths is different from those of armchair tubes. An analysis regarding the cross sectional shape has also been done. At some higher pressure, transition from circular to oval cross section takes place. This transition pressure is found to be equal 2.06GPa for (20,0) tube. Some comparison with chiral tubes has also been made and important differences on bond length behavior have been observed.