Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Chemistry of Nanoscale Semiconductor Clusters   The ground state structures of small silicon clusters are determined through
exhaustive tight-binding molecular dynamics simulation studies. These
simulations revealed that \Si{11} is an icosahedron with one missing cap,
\Si{12} is a complete icosahedron, \Si{13} is a surface capped icosahedron,
\Si{14} is a 4-4-4 layer structure with two caps, \Si{15} is a 1-5-3-5-1 layer
structure, and \Si{16} is a partially closed cage consisting of five-membered
rings. The characteristic feature of these clusters is that they are all
surface.
  Smalley and co-workers discovered that chemisorption reactivities of silicon
clusters vary over three orders of magnitude as a function of cluster size. In
particular, they found that \Si{33}, \Si{39}, and \Si{45} clusters are least
reactive towards various reagents compared to their immediate neighbors in
size. We provide insights into this observed reactivity pattern through our
stuffed fullerene model. This structural model consists of bulk-like core of
five atoms surrounded by fullerene-like surface. Reconstruction of the ideal
fullerene geometry gives rise to four-fold coordinated crown atoms and
$\pi$-bonded dimer pairs. This model yields unique structures for \Si{33},
\Si{39}, and \Si{45} clusters without any dangling bonds and thus explains
their lowest reactivity towards chemisorption of closed shell reagents. We also
explain why a) these clusters are substantially unreactive compared to bulk
surfaces and b) dissociative chemisorption occurs on bulk surfaces while
molecular chemisorption occurs on cluster surfaces. Finally, experiments on
Si$_x$X$_y$ (X = B, Al, Ga, P, As, AlP, GaAs) are suggested as a means of
verifying the proposed model.

27
The categories of this paper are: comp-gas
28
The categories of this paper are: alg-geom
33
The categories of this paper are: plasm-ph
0
The categories of this paper are: hep-ph
2
The categories of this paper are: math
1
The categories of this paper are: cs
6
The categories of this paper are: astro-ph
20
The categories of this paper are: acc-phys
29
The categories of this paper are: funct-an
15
The categories of this paper are: nucl-ex
22
The categories of this paper are: chao-dyn
10
The categories of this paper are: q-bio
8
The categories of this paper are: hep-ex
30
The categories of this paper are: q-alg
11
The categories of this paper are: hep-lat
7
The categories of this paper are: hep-th