  We show that transport in low-dimensional carbon structures with finite
concentrations of scatterers can be modeled by utilising scaling theory and
effective cross sections. Our reults are based on large scale numerical
simulations of carbon nanotubes and graphene nanoribbons, using a tightbinding
model with parameters obtained from first principles electronic structure
calculations. As shown by a comprehensive statistical analysis, the scattering
cross sections can be used to estimate the conductance of a quasi-1D system
both in the Ohmic and localized regimes. They can be computed with good
accuracy from the transmission functions of single defects, greatly reducing
the computational cost and paving the way towards using first principles
methods to evaluate the conductance of mesoscopic systems, consisting of
millions of atoms.
