Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Sc20C60: A Volleyballene   Since the discovery of the fullerene C60, many very interesting structures
have been proposed, such as Ti8C12, Au20, Au32, Au42, TM@Sin, Eu@Si20, B80, and
B_{40}^{-/0}. Here, an exceptionally stable hollow cage containing 20 scandiums
and 60 carbons was identified. This Sc20C60 molecular cluster has a Th point
group symmetry and a volleyball-like shape, that we refer to below as
Volleyballene. Electronic structure analysis shows that the formation of
delocalized {\pi} bonds between Sc atoms and neighboring five-membered carbon
rings is crucial for stabilizing the cage structure. A relatively large
HOMO-LUMO gap was found. The results of vibrational frequency analysis and
molecular dynamics simulations also demonstrate that this Volleyballene
molecule is exceptionally stable.

19
The categories of this paper are: eess
34
The categories of this paper are: chem-ph
33
The categories of this paper are: plasm-ph
28
The categories of this paper are: alg-geom
0
The categories of this paper are: hep-ph
37
The categories of this paper are: supr-con
1
The categories of this paper are: cs
5
The categories of this paper are: gr-qc
13
The categories of this paper are: quant-ph
2
The categories of this paper are: math
15
The categories of this paper are: nucl-ex
32
The categories of this paper are: atom-ph
20
The categories of this paper are: acc-phys
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
11
The categories of this paper are: hep-lat