Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Electronic Structure of the Complex Hydride NaAlH4   Density functional calculations of the electronic structure of the complex
hydride NaAlH4 and the reference systems NaH and AlH3 are reported. We find a
substantially ionic electronic structure for NaAlH4, which emphasizes the
importance of solid state effects in this material. The relaxed hydrogen
positions in NaAlH4 are in good agreement with recent experiment. The
electronic structure of AlH3 is also ionic. Implications for the binding of
complex hydrides are discussed.

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The categories of this paper are: math-ph
6
The categories of this paper are: astro-ph
30
The categories of this paper are: q-alg
35
The categories of this paper are: mtrl-th
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The categories of this paper are: cmp-lg
26
The categories of this paper are: bayes-an
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The categories of this paper are: hep-ex
32
The categories of this paper are: atom-ph
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The categories of this paper are: supr-con
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The categories of this paper are: hep-lat
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The categories of this paper are: nucl-th
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The categories of this paper are: math
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The categories of this paper are: hep-th
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The categories of this paper are: plasm-ph
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The categories of this paper are: nucl-ex
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The categories of this paper are: physics