Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First-principle study on the electronic and optical properties of
  cavities occupancy of SI methane hydrates   The electronic density of state and optical properties of the SI methane
hydrates with three different configurations are calculated by first-principle,
including (abbreviated as cI, similarly hereinafter), each cage is fully filled
with only one methane molecule; (cII), only one of the small cage lacks its
unique methane molecule; (cIII), only one large cage lacks its unique methane
molecule. The results show that the hydrate is most stable in the cI due to its
perfect structure, the cII is less stable, whereas the cIII is least stable
owing to its larger structural distortion after the loss of methane. On the
contrary, loss of a methane from cII causes negligible deformation. The
electronic density of states and the energy band gap of the cII is almost the
same with those of cI, differing obviously with those of cIII. Methane hydrate
is only responsive to light in the ultraviolet region, revealing their similar
properties, regardless of their structural discrepancies, or/and the different
ratios of water and methane molecules, 46/8=5.75 versus 46/7=6.57. Our
calculations demonstrate that the lack of one methane in the cII causes
negligible influence to the lattice structure and therefore to the electronic
and optical properties in comparison with the cI, whereas the lack of one
methane in the cIII can cause detectable changes. These results might provide
valuable reference to the industrial exploration.

5
The categories of this paper are: gr-qc
31
The categories of this paper are: ao-sci
0
The categories of this paper are: hep-ph
17
The categories of this paper are: q-fin
9
The categories of this paper are: nlin
30
The categories of this paper are: q-alg
6
The categories of this paper are: astro-ph
23
The categories of this paper are: solv-int
8
The categories of this paper are: hep-ex
2
The categories of this paper are: math
21
The categories of this paper are: adap-org
7
The categories of this paper are: hep-th
36
The categories of this paper are: cmp-lg
29
The categories of this paper are: funct-an
3
The categories of this paper are: physics
19
The categories of this paper are: eess