Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Plasmonic excitations in quantum-sized sodium nanoparticles studied by
  time-dependent density functional calculations   The plasmonic properties of sphere-like bcc Na nanoclusters ranging from
Na$_{15}$ to Na$_{331}$ have been studied by real-time time-dependent local
density approximation calculations. The optical absorption spectrum, density
response function and static polarizability are evaluated. It is shown that the
effect of the ionic background (ionic species and lattice) of the clusters
accounts for the remaining discrepancy in the principal (surface plasmon)
absorption peak energy between the experiments and previous calculations based
on a jellium background model. The ionic background effect also pushes the
critical cluster size where the maximum width of the principal peak occurs from
Na$_{40}$ predicted by the previous jellium model calculations to Na$_{65}$. In
the volume mode clusters (Na$_{27}$, Na$_{51}$, Na$_{65}$, Na$_{89}$ and
Na$_{113}$) in which the density response function is dominated by an intense
volume mode, a multiple absorption peak structure also appears next to the
principal peak. In contrast, the surface mode clusters of greater size
(Na$_{169}$, Na$_{229}$, Na$_{283}$ and Na$_{331}$) exhibit a smoother and
narrower principal absorption peak because their surface plasmon energy is
located well within that of the unperturbed electron-hole transitions, and
their density responses already bear resemblance to that of classical Mie
theory. Moreover, it is found that the volume plasmon that exist only in finite
size particles, gives rise to the long absorption tail in the UV region. This
volume plasmon manifests itself in the absorption spectrum even for clusters as
large as Na$_{331}$ with an effective diameter of $\sim$3.0 nm.

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The categories of this paper are: bayes-an
15
The categories of this paper are: nucl-ex
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
12
The categories of this paper are: nucl-th
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The categories of this paper are: solv-int
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The categories of this paper are: acc-phys
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The categories of this paper are: funct-an
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The categories of this paper are: quant-ph
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The categories of this paper are: astro-ph
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The categories of this paper are: math-ph
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The categories of this paper are: patt-sol
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The categories of this paper are: chem-ph
7
The categories of this paper are: hep-th
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The categories of this paper are: cmp-lg