Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Direct evidence of tungsten clustering in
  W$_{\text{0.02}}$V$_{\text{0.98}}$O$_{\text{2}}$ thin films and its effect on
  the metal-to-insulator transition   Substitutional tungsten doping of VO$_{\text{2}}$ thin films and its effect
on the metal-to-insulator transition are investigated by means of X-ray
diffraction, Cs-corrected scanning transmission electron microscope (STEM) and
ab-initio simulations. The W$_{\text{0.02}}$V$_{\text{0.98}}$O$_{\text{2}}$
thin films deposited on (001) sapphire are studied in both planar and
transverse geometries. The tungsten atoms are distinguishable from the V atoms
in the Z-sensitive high angle annular dark field (HAADF) STEM image and their
nature is further confirmed by electron energy loss spectroscopy (EELS). The W
dopants are found to substitute in the V sites and form local clusters at first
neighbour, preferentially along the <010>$_{\text{R}}$ directions. Ab-initio
modeling for this 2 at.% W doped VO$_{\text{2}}$ confirms the experimentally
found W clustering mechanism to be the most stable substitutional configuration
and it demonstrates that the binding energy of such cluster is 0.18 eV. Driving
forces for short range ordering are also obtained along the <011>$_{\text{R}}$
and <110>$_{\text{R}}$ directions. Strong energetic penalty is found for the
<001>$_{\text{R}}$ direction. Simulations indicate that the clustering helps in
stabilizing the tetragonal structure, while a diluted W dopant induces more
structural distortion and V-V pairing.This suggests that the clustering
mechanism plays a critical role in the transition temperature evolution with
the W dopants.

33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
10
The categories of this paper are: q-bio
30
The categories of this paper are: q-alg
28
The categories of this paper are: alg-geom
32
The categories of this paper are: atom-ph
0
The categories of this paper are: hep-ph
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
2
The categories of this paper are: math
37
The categories of this paper are: supr-con
35
The categories of this paper are: mtrl-th
8
The categories of this paper are: hep-ex
26
The categories of this paper are: bayes-an
9
The categories of this paper are: nlin
20
The categories of this paper are: acc-phys