Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Potential super-hard Osmium di-nitride with fluorite structure:
  First-principles calculations   We have performed systematic first-principles calculations on di-carbide,
-nitride, -oxide and -boride of platinum and osmium with the fluorite
structure. It is found that only PtN$_{2}$, OsN$_{2}$ and OsO$_{2}$ are
mechanically stable. In particular OsN$_{2}$ has the highest bulk modulus of
360.7 GPa. Both the band structure and density of states show that the new
phase of OsN$_{2}$ is metallic. The high bulk modulus is owing to the strong
covalent bonding between Os 5\textit{d} and N 2\textit{p} states and the dense
packed fluorite structure.

29
The categories of this paper are: funct-an
31
The categories of this paper are: ao-sci
17
The categories of this paper are: q-fin
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
33
The categories of this paper are: plasm-ph
25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
16
The categories of this paper are: stat
37
The categories of this paper are: supr-con
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
28
The categories of this paper are: alg-geom
19
The categories of this paper are: eess
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin