Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First-principles study on the electronic and transport properties of
  periodically nitrogen-doped graphene and carbon nanotube superlattices   Prompted by recent reports on $\sqrt{3} \times \sqrt{3}$ graphene
superlattices with intrinsic inter-valley interactions, we perform
first-principles calculations to investigate the electronic properties of
periodically nitrogen-doped graphene and carbon nanotube nanostructures. In
these structures, nitrogen atoms substitute one-sixth of the carbon atoms in
the pristine hexagonal lattices with exact periodicity to form perfect
$\sqrt{3} \times \sqrt{3}$ superlattices of graphene and carbon nanotubes.
Multiple nanostructures of $\sqrt{3} \times \sqrt{3}$ graphene ribbons and
carbon nanotubes are explored, and all configurations show nonmagnetic and
metallic behaviors. The transport properties of $\sqrt{3} \times \sqrt{3}$
graphene and carbon nanotube superlattices are calculated utilizing the
non-equilibrium Green's function formalism combined with density functional
theory. The transmission spectrum through the pristine and $\sqrt{3} \times
\sqrt{3}$ armchair carbon nanotube heterostructure shows quantized behavior
under certain circumstances.

14
The categories of this paper are: math-ph
26
The categories of this paper are: bayes-an
33
The categories of this paper are: plasm-ph
29
The categories of this paper are: funct-an
28
The categories of this paper are: alg-geom
16
The categories of this paper are: stat
36
The categories of this paper are: cmp-lg
18
The categories of this paper are: econ
2
The categories of this paper are: math
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
24
The categories of this paper are: dg-ga
34
The categories of this paper are: chem-ph
12
The categories of this paper are: nucl-th
0
The categories of this paper are: hep-ph
23
The categories of this paper are: solv-int