Modeling and characterizing single-walled carbon nanotubes by pressure probe

TL;DR

This study investigates how hydrostatic pressure affects the structural properties of single-walled carbon nanotubes, revealing that pressure-induced changes in bond lengths and shape transitions can be used to characterize different nanotube types.

Contribution

The paper introduces a detailed numerical analysis of pressure effects on SWNTs, showing how bond lengths and shape transitions serve as effective probes for nanotube characterization.

Findings

Bond lengths fully describe achiral SWNT structure.

Pressure causes shape transition from circular to oval.

Chiral angle influences bond length behavior under pressure.

Abstract

We compare the behavior of bond lengths, cross sectional shape and bulk modulus in equilibrium structure at ambient conditions and under hydrostatic pressure of all the three kinds of uncapped single walled carbon nanotubes. Results of our numerical calculations show that two bond lengths completely describe the structure of achiral SWNT whereas only one bond length is required to determine structure of chiral SWNT. In armchair tubes, one bond length is found to be larger than that of graphitic value while in zigzag tubes one bond length has a constant value. These bond lengths are very sensitive to tube radius. In chiral tubes, the value of bond length is found to depend on the chirality and slightly on the tube radius. Different responses of these bond lengths are found on application of pressure. At some critical pressure, both bond lengths become equal to each other in achiral tubes. An analysis regarding the cross sectional shape of the nanotubes and its pressure dependence has also been done. The shape transition, from circular to oval shape takes place. At this transition, the behavior of bond lengths is found different and dependent on the chirality of the tubes. Chiral tubes with chiral angle which is mid way between zigzag and armchair tubes are found to have most prominent effects of chirality. Thus we demonstrate that pressure is a useful probe to characterize various kinds of carbon nanotubes.