Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Vibrational properties of sodosilicate glasses from first-principles
  calculations   The vibrational properties of three sodosilicate glasses have been
investigated in the framework of Density Functional Theory. The pure
vibrational density of states has been calculated for all systems and the
different vibrational modes have been assigned to specific atoms or structural
units. It is shown that the Na content affects several vibrational features as
the position and intensity of the $R$ band or the mixing of the rocking and
bending atomic motions of the Si-O-Si bridges. The calculated Raman spectra
have been found to agree with experimental observations and their decomposition
indicated the dominant character of the non-bridging oxygen contribution on the
spectra, in particular for the high-frequency band, above 800~cm$^{-1}$.
  The decomposition of the high-frequency Raman feature into vibrations of the
depolymerized tetrahedra (i.e. $Q_n$-units) has revealed spectral shapes of the
partial contributions that cannot be accounted for by simple gaussians as
frequently assumed in the treatment of experimentally obtained Raman spectra.

34
The categories of this paper are: chem-ph
3
The categories of this paper are: physics
35
The categories of this paper are: mtrl-th
25
The categories of this paper are: patt-sol
12
The categories of this paper are: nucl-th
30
The categories of this paper are: q-alg
13
The categories of this paper are: quant-ph
24
The categories of this paper are: dg-ga
22
The categories of this paper are: chao-dyn
11
The categories of this paper are: hep-lat
32
The categories of this paper are: atom-ph
14
The categories of this paper are: math-ph
23
The categories of this paper are: solv-int
5
The categories of this paper are: gr-qc
28
The categories of this paper are: alg-geom
2
The categories of this paper are: math