Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: First-Principles Theory of Multipolar Order in Neptunium Dioxide   We provide a first-principle, materials-specific theory of multipolar order
and superexchange in NpO$_2$ by means of a non-collinear local-density
approximation +$U$ (LDA+$U$) method. Our calculations offer a precise
microscopic description of the triple-$q$-antiferro ordered phase in the
absence of any dipolar moment. We find that, while the most common non-dipolar
degrees of freedom (e.g., electric quadrupoles and magnetic octupoles) are
active in the ordered phase, both the usually neglected higher-order multipoles
(electric hexadecapoles and magnetic triakontadipoles) have at least an equally
significant effect.

23
The categories of this paper are: solv-int
1
The categories of this paper are: cs
20
The categories of this paper are: acc-phys
26
The categories of this paper are: bayes-an
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The categories of this paper are: alg-geom
30
The categories of this paper are: q-alg
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The categories of this paper are: atom-ph
29
The categories of this paper are: funct-an
25
The categories of this paper are: patt-sol
14
The categories of this paper are: math-ph
31
The categories of this paper are: ao-sci
24
The categories of this paper are: dg-ga
9
The categories of this paper are: nlin
6
The categories of this paper are: astro-ph
12
The categories of this paper are: nucl-th
21
The categories of this paper are: adap-org