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Water Nanoconfined in Clays: The Structure of Na Vermiculite Revisited by Ab Initio Simulations
journal contribution
posted on 2013-08-01, 00:00 authored by Pierfranco Demontis, Marco Masia, Giuseppe B. SuffrittiThe
results of Car–Parrinello molecular dynamics simulations
of vermiculite clay at the hydration level found in the natural mineral
(4 H2O per Na+) are reported. The structure
and the vibrational spectrum of the aluminosilicate layer is well
reproduced by the simulations. As for the structure of the Na+ cations and of water molecules adsorbed in the interlayer,
the ones proposed in X-ray diffraction experimental papers are not
in full agreement with the results of neutron diffraction experiments
found in literature, yielding only the density profile perpendicular
to the aluminosilicate layers, but including hydrogens. Our calculations
result in a structure of the interlayer content, which is in agreement
with the neutron-diffraction density profile, and yet compatible with
X-ray diffraction data. Some features of the adsorbed water resulting
from the simulation are an example of incomplete cation hydration
and can be of general interest.
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Ab Initio SimulationsThe resultsdensity profilewater Nanoconfinedcalculations resultvermiculite clayvibrational spectrumwater moleculesneutron diffraction experimentsaluminosilicate layerhydration levelinterlayer content2ONa Vermiculite Revisitedcation hydrationdynamics simulationsaluminosilicate layers