Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Elasticity and piezoelectricity of zinc oxide crystals, single layers,
  and possible single-walled nanotubes   The elasticity and piezoelectricity of zinc oxide (ZnO) crystals and single
layers are investigated from the first-principles calculations. It is found
that a ZnO thin film less than three Zn-O layers prefers a planar graphite-like
structure to the wurtzite structure. ZnO single layers are much more flexible
than graphite single layers in the elasticity and stronger than boron nitride
single layers in the piezoelectricity. Single-walled ZnO nanotubes (SWZONTs)
can exist in principle because of their negative binding energy. The
piezoelectricity of SWZONTs depends on their chirality. For most ZnO nanotubes
except the zigzag type, twists around the tube axis will induce axial
polarizations. A possible scheme is proposed to achieve the SWZONTs from the
solid-vapor phase process with carbon nanotubes as templates.

23
The categories of this paper are: solv-int
18
The categories of this paper are: econ
19
The categories of this paper are: eess
2
The categories of this paper are: math
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
7
The categories of this paper are: hep-th
21
The categories of this paper are: adap-org
33
The categories of this paper are: plasm-ph
10
The categories of this paper are: q-bio
1
The categories of this paper are: cs
34
The categories of this paper are: chem-ph
16
The categories of this paper are: stat
15
The categories of this paper are: nucl-ex
17
The categories of this paper are: q-fin
20
The categories of this paper are: acc-phys