Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Evidence for a new extended solid of nitrogen   A new extended solid nitrogen, referred to post-layered-polymeric nitrogen
(PLP-N), was observed by further heating the layered-polymeric nitrogen (LP-N)
to above 2300 K at 161 GPa. The new phase is found to be very transparent and
exhibits ultra-large d-spacings ranging from 2.8 to 4.9 {\AA} at 172 GPa,
suggesting a possible large-unit-cell 2D chain-like or 0D cluster-type
structure with wide bandgap. However, the observed X-ray diffraction pattern
and Raman scattering data cannot match any predicted structures in the
published literature. This finding further complicates the phase diagram of
nitrogen and also highlights the path dependence of the high-pressure
dissociative transition in nitrogen. In addition, the forming boundary between
cg-N and LP-N has been determined.

29
The categories of this paper are: funct-an
10
The categories of this paper are: q-bio
14
The categories of this paper are: math-ph
16
The categories of this paper are: stat
20
The categories of this paper are: acc-phys
5
The categories of this paper are: gr-qc
36
The categories of this paper are: cmp-lg
32
The categories of this paper are: atom-ph
21
The categories of this paper are: adap-org
19
The categories of this paper are: eess
35
The categories of this paper are: mtrl-th
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
24
The categories of this paper are: dg-ga
17
The categories of this paper are: q-fin
30
The categories of this paper are: q-alg