Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Probing the sp^2 dependence of elastic moduli in ultrahard diamond films   The structural and elastic properties of diamond nanocomposites and
ultrananocrystalline diamond films (UNCD) are investigated using both empirical
potentials and tight binding schemes. We find that both materials are extremely
hard, but their superb diamondlike properties are limited by their sp^2
component. In diamond composites, the sp^2 atoms are found in the matrix and
far from the interface with the inclusion, and they are responsible for the
softening of the material. In UNCD, the sp^2 atoms are located in the grain
boundaries. They offer relaxation mechanisms which relieve the strain but, on
the other hand, impose deformations that lead to softening. The higher the sp^2
component the less rigid these materials are.

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The categories of this paper are: atom-ph
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The categories of this paper are: nlin
8
The categories of this paper are: hep-ex
21
The categories of this paper are: adap-org
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The categories of this paper are: eess
7
The categories of this paper are: hep-th
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The categories of this paper are: funct-an
0
The categories of this paper are: hep-ph
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The categories of this paper are: ao-sci
25
The categories of this paper are: patt-sol
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The categories of this paper are: math-ph
13
The categories of this paper are: quant-ph
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The categories of this paper are: comp-gas
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The categories of this paper are: plasm-ph
2
The categories of this paper are: math
5
The categories of this paper are: gr-qc