Characterizing single-walled carbon nanotubes by pressure probe

We compare the behavior of bond lengths, cross sectional shape and bulk modulus at ambient conditions and under hydrostatic pressure of all the three kinds of long uncapped single-walled carbon nanotubes. Results show that two bond lengths completely describe the structure of armchair and zigzag tubes (non-chiral), whereas only one bond length is required to define structure of chiral tubes. In armchair tubes, one bond length is found to be larger and the other smaller than the value for graphene, while in zigzag tubes one of the bond lengths remains equal to and the other larger than graphene bond length. In chiral tubes, three bond lengths are found to be equal to each other and their value depends on the chirality. At some critical pressure values depending on radius, both bond lengths become equal to each other in non-chiral tubes. Above these critical pressure values, the cross section shape changes from circular to oval and the pattern of bond lengths becomes different and dependent on the chirality of the tubes.