Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Composition, structure, and stability of the rutile TiO_2(110) surface:
  oxygen depletion, hydroxylation, hydrogen migration and water adsorption   A comprehensive phase diagram of lowest-energy structures and compositions of
the rutile TiO_2(110) surface in equilibrium with a surrounding gas phase at
finite temperatures and pressures has been determined using density functional
theory in combination with a thermodynamic formalism. The exchange of oxygen,
hydrogen, and water molecules with the gas phase is considered. Particular
attention is given to the convergence of all calculations with respect to
lateral system size and slab thickness. In addition, the reliability of
semilocal density functionals to describing the energetics of the reduced
surfaces is critically evaluated. For ambient conditions the surface is found
to be fully covered by molecularly adsorbed water. At low coverages, in the
limit of single, isolated water molecules, molecular and dissociative
adsorption become energetically degenerate. Oxygen vacancies form in strongly
reducing, oxygen-poor environments. However, already at slightly more moderate
conditions it is shown that removing full TiO_2 units from the surface is
thermodynamically preferred. In agreement with recent experimental observations
it is furthermore confirmed that even under extremely hydrogen-rich
environments the surface cannot be fully hydroxylated, but only a maximum
coverage with hydrogen of about 0.6-0.7 monolayer can be reached. Finally,
calculations of migration paths strongly suggest that hydrogen prefers to
diffuse into the bulk over desorbing from the surface into the gas phase.

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The categories of this paper are: chem-ph
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The categories of this paper are: adap-org
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The categories of this paper are: mtrl-th
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The categories of this paper are: eess
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The categories of this paper are: nlin
3
The categories of this paper are: physics
8
The categories of this paper are: hep-ex
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The categories of this paper are: nucl-th
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The categories of this paper are: q-bio
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The categories of this paper are: nucl-ex
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The categories of this paper are: econ
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The categories of this paper are: math-ph
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The categories of this paper are: cmp-lg
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The categories of this paper are: atom-ph
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The categories of this paper are: plasm-ph
2
The categories of this paper are: math