Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Density, structure and dynamics of water: the effect of Van der Waals
  interactions   It is known that ab initio molecular dynamics (AIMD) simulations of liquid
water, based on the generalized gradient approximation (GGA) to density
functional theory (DFT), yield structural and diffusive properties in
reasonable agreement with experiment only if artificially high temperatures are
used in the simulations. The equilibrium density, at normal conditions, of DFT
water has been recently shown by Schmidt et al. [J. Phys. chem. B, 113, 11959
(2009)] to be underestimated by different GGA functionals for exchange and
correlation, and corrected by the addition of interatomic pair potentials to
describe van derWaals (vdW) interactions. In this contribution we present a
DFTAIMD study of liquid water using several GGA functionals as well as the van
der Waals density functional (vdW-DF) of Dion et al. [Phys. Rev. Lett. 92,
246401(2004)]. As expected, we find that the density of water is grossly
underestimated by GGA functionals. When a vdW-DF is used, the density improves
drastically and the experimental diffusivity is reproduced without the need of
thermal corrections. We analyze the origin of the density differences between
all the functionals. We show that the vdW-DF increases the population of
non-H-bonded interstitial sites, at distances between the first and second
coordination shells. However, it excessively weakens the H-bond network,
collapsing the second coordination shell. This structural problem is partially
associated to the choice of GGA exchange in the vdW-DF. We show that a
different choice for the exchange functional is enough to achieve an overall
improvement both in structure and diffusivity.

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The categories of this paper are: hep-ex
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The categories of this paper are: quant-ph
36
The categories of this paper are: cmp-lg
1
The categories of this paper are: cs
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The categories of this paper are: nlin
33
The categories of this paper are: plasm-ph
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The categories of this paper are: hep-ph
19
The categories of this paper are: eess
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The categories of this paper are: gr-qc
32
The categories of this paper are: atom-ph
28
The categories of this paper are: alg-geom
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The categories of this paper are: acc-phys
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The categories of this paper are: comp-gas
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The categories of this paper are: math-ph
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The categories of this paper are: q-fin
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The categories of this paper are: funct-an