Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Concerted Metal Cation Desorption and Proton Transfer on Deprotonated
  Silica Surfaces   The adsorption equilibrium constants of monovalent and divalent cations to
material surfaces in aqueous media are central to many technological, natural,
and geochemical processes. Cation adsorption/desorption is often proposed to
occur in concert with proton-transfer on hydroxyl-covered mineral surfaces, but
so far this cooperative effect has been inferred indirectly. This work applies
Density Functional Theory (DFT)-based molecular dynamics simulations of
explicit liquid water/mineral interfaces to calculate metal ion desorption free
energies. Monodentate adsorption of Na(+), Mg(2+), and Cu(2+) on partially
deprotonated silica surfaces are considered. Na(+) is predicted to be unbound,
while Cu(2+) exhibits larger binding free energies to surface SiO(-) groups
than Mg(2+). The predicted trends agree with competitive adsorption
measurements on fumed silica surfaces. As desorption proceeds, Cu(2+)
dissociates one of the H2O molecules in its first solvation shell, turning into
Cu(2+)O(-)(H2O)(3), while Mg remains Mg(2+)(H2O)(6). The protonation state of
the SiO(-) group at the initial binding site does not vary monotonically with
cation desorption.

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The categories of this paper are: funct-an
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The categories of this paper are: comp-gas
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The categories of this paper are: chao-dyn
5
The categories of this paper are: gr-qc
1
The categories of this paper are: cs
14
The categories of this paper are: math-ph
34
The categories of this paper are: chem-ph
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The categories of this paper are: acc-phys
7
The categories of this paper are: hep-th
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The categories of this paper are: econ
15
The categories of this paper are: nucl-ex
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The categories of this paper are: cmp-lg
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The categories of this paper are: patt-sol
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The categories of this paper are: atom-ph
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The categories of this paper are: stat
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The categories of this paper are: dg-ga