Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: The Influence of Gradient Corrections on Bulk and Surface Properties of
  TiO2 and SnO2   First-principles calculations based on density functional theory and the
pseudo\-potential method have been used to investigate the influence of
gradient corrections to the standard LDA technique on the equilibrium structure
and energetics of rutile TiO$_2$ and SnO$_2$ perfect crystals and their (110)
surfaces. We find that gradient corrections increase the calculated lattice
parameters by roughly 3~\%, as has been found for other types of material.
Gradient corrections give only very minor changes to the equilibrium surface
structure, but reduce the surface energies by about 30~\%.

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The categories of this paper are: math-ph
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The categories of this paper are: alg-geom
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The categories of this paper are: solv-int
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The categories of this paper are: quant-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
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The categories of this paper are: dg-ga
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The categories of this paper are: plasm-ph
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The categories of this paper are: q-alg
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The categories of this paper are: bayes-an
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The categories of this paper are: nucl-th
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The categories of this paper are: cmp-lg
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The categories of this paper are: stat
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The categories of this paper are: nucl-ex
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The categories of this paper are: ao-sci
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The categories of this paper are: q-bio