Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Selecting the suitable dopants: electronic structures of transition
  metal and rare earth doped thermoelectric sodium cobaltate   Engineered $Na_{0.75}CoO_2$ is considered a prime candidate to achieve
high-efficiency thermoelectric systems to regenerate electricity from waste
heat. In this work, three elements with outmost electronic configurations, (1)
an open d shell (Ni), (2) a closed d shell (Zn), and (3) a half filled f shell
(Eu) with maximum unpaired electrons, were selected to outline the dopants'
effects on electronic and crystallographic structures of $Na_{0.75}CoO_2$.
Systematic $ab$ $initio$ density functional calculations with $DMOL^3$ package
showed that the Ni and Zn were more stable when substituting Co with formation
energy $-2.35$ eV, $2.08$ eV when Fermi level equals to the valence band
maximum. While Eu is more stable when it substitutes Na having formation energy
of $-2.64$ eV. As these results show great harmony with existing experimental
data, they provide new insights into the fundamental principle of dopant
selection for manipulating the physical properties in the development of
high-performance sodium cobaltate based multifunctional materials.

25
The categories of this paper are: patt-sol
1
The categories of this paper are: cs
9
The categories of this paper are: nlin
17
The categories of this paper are: q-fin
21
The categories of this paper are: adap-org
20
The categories of this paper are: acc-phys
32
The categories of this paper are: atom-ph
22
The categories of this paper are: chao-dyn
8
The categories of this paper are: hep-ex
5
The categories of this paper are: gr-qc
14
The categories of this paper are: math-ph
10
The categories of this paper are: q-bio
16
The categories of this paper are: stat
28
The categories of this paper are: alg-geom
35
The categories of this paper are: mtrl-th
11
The categories of this paper are: hep-lat