Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Mechanical properties and electronic structure of the incompressible
  rhenium carbides and nitrides: A first-principles study   By means of first-principles calculations, the structural stability,
mechanical properties and electronic structure of the newly synthesized
incompressible Re2C, Re2N, Re3N and an analogous compound Re3C have been
investigated. Our results agree well with the available experimental and
theoretical data. The proposed Re3C is shown to be energetically, mechanically
and dynamically stable and also incompressible. Furthermore, it is suggested
that the incompressibility of these compounds is originated from the strong
covalent bonding character with the hybridization of 5d orbital of Re and the
2p orbital of C or N, and a zigzag topology of interconnected bonds, e.g.,
Re-Re, Re-C or Re-N bonding.

30
The categories of this paper are: q-alg
8
The categories of this paper are: hep-ex
22
The categories of this paper are: chao-dyn
7
The categories of this paper are: hep-th
25
The categories of this paper are: patt-sol
16
The categories of this paper are: stat
33
The categories of this paper are: plasm-ph
9
The categories of this paper are: nlin
24
The categories of this paper are: dg-ga
35
The categories of this paper are: mtrl-th
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
27
The categories of this paper are: comp-gas
2
The categories of this paper are: math
14
The categories of this paper are: math-ph
15
The categories of this paper are: nucl-ex