Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Work functions of pristine and alkali-metal intercalated carbon
  nanotubes and bundles   The work functions (WF) of single-walled carbon nanotubes and bundles are
studied using first principles methods. For individual metallic tubes, the WF
is independent of the chirality and increase slightly with tube diameter. For
semiconducting tubes, the WF (as defined by the HOMO energy) decreases rapidly.
The WF of nanotube bundles ($\sim$ 5 eV) shows no clear dependence on the tube
size and chirality, slightly higher than individual tubes. Calculations on
finite tubes show no substantial difference in the tube end and the side wall.
Upon alkali-metal intercalation, the WF decreases dramatically and the
electronic states near the Fermi level are significantly modified. The metallic
and semiconducting nanotubes bundles become indistinguishable.

9
The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
37
The categories of this paper are: supr-con
19
The categories of this paper are: eess
6
The categories of this paper are: astro-ph
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
15
The categories of this paper are: nucl-ex
34
The categories of this paper are: chem-ph
20
The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
32
The categories of this paper are: atom-ph
3
The categories of this paper are: physics