Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Understanding the nature of "superhard graphite"   Numerous experiments showed that on cold compression graphite transforms into
a new superhard and transparent allotrope. Several structures with different
topologies have been proposed for this phase. While experimental data are
consistent with these models, the only way to solve this puzzle is to find
which structure is kinetically easiest to form. Using state-of-the-art
molecular-dynamics transition path sampling simulations, we investigate kinetic
pathways of the pressure-induced transformation of graphite to various
superhard candidate structures. Unlike hitherto applied methods for elucidating
nature of superhard graphite, transition path sampling realistically models
nucleation events necessary for physically meaningful transformation kinetics.
We demonstrate that nucleation mechanism and kinetics lead to $M$-carbon as the
final product. $W$-carbon, initially competitor to $M$-carbon, is ruled out by
phase growth. Bct-C$_4$ structure is not expected to be produced by cold
compression due to less probable nucleation and higher barrier of formation.

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The categories of this paper are: hep-th
32
The categories of this paper are: atom-ph
25
The categories of this paper are: patt-sol
37
The categories of this paper are: supr-con
34
The categories of this paper are: chem-ph
17
The categories of this paper are: q-fin
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
31
The categories of this paper are: ao-sci
29
The categories of this paper are: funct-an
27
The categories of this paper are: comp-gas
23
The categories of this paper are: solv-int
12
The categories of this paper are: nucl-th
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio