Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Structures of Si and Ge nanowires in the sub-nanometer range   We report an ab-initio investigation of several possible Si and Ge pristine
nanowires with diameters between 0.5 and 1.2 nm. We considered nanowires based
on the diamond structure, high-density bulk structures, and fullerene-like
structures. We find that the diamond structure nanowires are unstable for
diameters smaller than 1 nm, and undergo considerable structural
transformations towards amorphous-like wires. Such instability is consistent
with a continuum model that predicts, for both Si and Ge, a stability crossover
between diamond and high-density-structure nanowires for diameters smaller than
1 nm. For diameters between 0.8 nm and 1 nm, filled-fullerene wires are the
most stable ones. For even smaller diameters (d~0.5 nm), we find that a simple
hexagonal structure is particularly stable for both Si and Ge.

37
The categories of this paper are: supr-con
8
The categories of this paper are: hep-ex
1
The categories of this paper are: cs
27
The categories of this paper are: comp-gas
33
The categories of this paper are: plasm-ph
31
The categories of this paper are: ao-sci
14
The categories of this paper are: math-ph
17
The categories of this paper are: q-fin
24
The categories of this paper are: dg-ga
23
The categories of this paper are: solv-int
30
The categories of this paper are: q-alg
21
The categories of this paper are: adap-org
26
The categories of this paper are: bayes-an
35
The categories of this paper are: mtrl-th
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph