Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Metastable quasi-one-dimensional ensembles of nitrogen clusters N_8   By means of ab initio and tight-binding calculations it is shown that
metastable nitrogen clusters N_8 (boats) can form quasi-one-dimensional
ensembles in which the nearest clusters N_8 are bound to each other by covalent
bonds. Those ensembles are characterized by rather high energy barriers (~ 0.3
eV) that prevent the fission of the ensembles into isolated N_8 clusters and/or
N_2 molecules.

18
The categories of this paper are: econ
20
The categories of this paper are: acc-phys
8
The categories of this paper are: hep-ex
33
The categories of this paper are: plasm-ph
7
The categories of this paper are: hep-th
14
The categories of this paper are: math-ph
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
34
The categories of this paper are: chem-ph
0
The categories of this paper are: hep-ph
22
The categories of this paper are: chao-dyn
12
The categories of this paper are: nucl-th
23
The categories of this paper are: solv-int
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess