SWCNTs	single-walled carbon nanotubes
PES	potential energy surface
TS	transition state
DFT	density functional theory
HF	Hartree–Fock
PBE	Perdew–Burke–Ernzerhof
O	Mulliken bond order
HOMO	high occupied molecular orbital
LUMO	low unoccupied molecular orbital
C	conformation of chair form
Tw	conformation of twist form