Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Ab initio investigation of the AlN:Er system   In the present study an ab initio investigation on the AlN:Er system for
concentrations of Er ranging from 0.78 to 12.5 % is presented. The
crystallographic localisation of the rare earth atoms in the wurtzite lattice
is determined, elucidating previously published experimental deductions, and
the existence of a solid solution in the AlN:Er system in this range is
confirmed. Er incorporation in the tetrahedral and octahedral insertion sites
is shown to be thermodynamically metastable and is found to induce shallow
states in the bandgaps. The effect of Er concentration on the lattice constants
and bandgaps and bandstructures of the ErxAl1-xN ternary compound is presented.
Finally, in accordance with experimental specifications, Er incorporation in
the AlNO system is also examined.

22
The categories of this paper are: chao-dyn
6
The categories of this paper are: astro-ph
13
The categories of this paper are: quant-ph
23
The categories of this paper are: solv-int
25
The categories of this paper are: patt-sol
0
The categories of this paper are: hep-ph
31
The categories of this paper are: ao-sci
12
The categories of this paper are: nucl-th
9
The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
11
The categories of this paper are: hep-lat
5
The categories of this paper are: gr-qc
17
The categories of this paper are: q-fin
16
The categories of this paper are: stat
29
The categories of this paper are: funct-an
18
The categories of this paper are: econ