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Peculiar structure of water in slightly superhydrated vermiculite clay studied by Car–Parrinello molecular dynamics simulations

Demontis, Pierfranco and Masia, Marco and Suffritti, Giuseppe Baldovino (2014) Peculiar structure of water in slightly superhydrated vermiculite clay studied by Car–Parrinello molecular dynamics simulations. The Journal of Physical Chemistry. C, Vol. 118 (15), p. 7923-7931. ISSN 1932-7447. eISSN 1932-7455. Article.

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DOI: 10.1021/jp409723x

Abstract

An unusual water structure was found using Car–Parrinello Molecular Dynamics simulations of a slightly superhydrated Na–vermiculite clay, containing six water molecules per sodium cation, corresponding to that of recent experiments performed to detect dynamical crossovers in the adsorbed supercooled water. In our simulations we observe that water forms two closed packed hexagonal plane layers parallel to aluminosilicate sheets and linked to their surface oxygens by hydrogen bonds. The presence of these hydrogen bonds and the coordination to Na cations lying midway between the clay layers, lowers the number of water–water hydrogen bonds, thus making the closed-packed structure thermodynamically accessible. Remarkably, we have found that this structure is stable across a wide range of temperatures. At the best of our knowledge, this kind of water structure was never reported before, except for a similar hexatic phase (liquid-like, but with a local hexagonal compact symmetry) resulting from a two-dimensional model of water proposed by Vilanova and Franzese.

Item Type:Article
ID Code:10241
Status:Published
Refereed:Yes
Uncontrolled Keywords:Car–Parrinello molecular dynamics simulations, water molecules, dynamical crossovers, hydrogen bonds
Subjects:Area 03 - Scienze chimiche > CHIM/02 Chimica fisica
Divisions:002 Altri enti e centri di ricerca del Nord Sardegna > SLACS-Sardinian Laboratory for Computational Materials Science, Cagliari
002 Altri enti e centri di ricerca del Nord Sardegna > CNR-Consiglio Nazionale delle Ricerche
002 Altri enti e centri di ricerca del Nord Sardegna > INSTM-Consorzio Interuniversitario Nazionale per la Scienza e la Tecnologia dei Materiali, Unità di ricerca di Sassari
001 Università di Sassari > 01-a Nuovi Dipartimenti dal 2012 > Chimica e Farmacia
Publisher:American Chemical Society
ISSN:1932-7447
eISSN:1932-7455
Deposited On:29 Oct 2014 18:11

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