Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: A direct view at excess electrons in TiO$_2$ rutile and anatase   A combination of Scanning Tunneling Microscopy/Spectroscopy and Density
Functional Theory (DFT+U) is used to characterize excess electrons in TiO$_2$
rutile and anatase, two prototypical materials with identical chemical
composition but different crystal lattices. In rutile, excess electrons can
localize at any lattice Ti atom, forming a small polaron, which can easily hop
to neighboring sites. In contrast, electrons in anatase prefer a free-carrier
state, and can only be trapped near oxygen vacancies or form shallow donor
states bound to Nb dopants. The present study conclusively explains the
differences between the two polymorphs and indicates that even small structural
variations in the crystal lattice can lead to a very different behavior.

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The categories of this paper are: acc-phys
10
The categories of this paper are: q-bio
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The categories of this paper are: q-alg
31
The categories of this paper are: ao-sci
36
The categories of this paper are: cmp-lg
6
The categories of this paper are: astro-ph
14
The categories of this paper are: math-ph
8
The categories of this paper are: hep-ex
13
The categories of this paper are: quant-ph
0
The categories of this paper are: hep-ph
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The categories of this paper are: chao-dyn
3
The categories of this paper are: physics
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The categories of this paper are: stat
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
18
The categories of this paper are: econ