  We theoretically investigate the influence of defect-induced long-range
deformations in carbon nanotubes on their electronic transport properties. To
this end we perform numerical ab-initio calculations using a
density-functional-based tight-binding (DFTB) model for various tubes with
vacancies. The geometry optimization leads to a change of the atomic positions.
There is a strong reconstruction of the atoms near the defect (called
"distortion") and there is an additional long-range deformation. The impact of
both structural features on the conductance is systematically investigated. We
compare short and long CNTs of different kinds with and without long-range
deformation. We find for the very thin (9,0)-CNT that the long-range
deformation additionally affects the transmission spectrum and the conductance
compared to the short-range lattice distortion. The conductance of the larger
(11,0)- or the (14,0)-CNT is overall less affected implying that the influence
of the long-range deformation decreases with increasing tube diameter.
Furthermore, the effect can be either positive or negative depending on the CNT
type and the defect type. Our results indicate that the long-range deformation
must be included in order to reliably describe the electronic structure of
defective, small-diameter zigzag tubes.
