Peculiar Structure of Water in Slightly Superhydrated Vermiculite Clay Studied by Car鈥揚arrinello Molecular Dynamics Simulations

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• 作者：Pierfranco Demontis ; Marco Masia ; Giuseppe B. Suffritti
• 刊名：Journal of Physical Chemistry C
• 出版年：2014
• 出版时间：April 17, 2014
• 年：2014
• 卷：118
• 期：15
• 页码：7923-7931
• 全文大小：452K
• 年卷期：v.118,no.15(April 17, 2014)
• ISSN：1932-7455

文摘

An unusual water structure was found using Car鈥揚arrinello Molecular Dynamics simulations of a slightly superhydrated Na鈥搗ermiculite 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鈥搘ater 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.