Water Release from Pyrophyllite during the Dehydroxylation Process Explored by Quantum Mechanical Simulations

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• 作者：Esther Molina-Montes ; Davide Donadio ; Alfonso Hern谩ndez-Laguna ; Michele Parrinello ; C. Ignacio Sainz-D铆az
• 刊名：The Journal of Physical Chemistry C
• 出版年：2013
• 出版时间：April 18, 2013
• 年：2013
• 卷：117
• 期：15
• 页码：7526-7532
• 全文大小：331K
• 年卷期：v.117,no.15(April 18, 2013)
• ISSN：1932-7455

文摘

We have investigated one of the most controversial aspects of the dehydroxylation鈥搑ehydroxylation process of dioctahedral 2:1 phyllosilicates, that is the release of water from the internal structure of the mineral. We simulate the release of water from a periodic crystal model of pyrophyllite by Car鈥揚arrinello molecular dynamics based on Density Functional Theory. The metadynamics algorithm is employed to accelerate activated processes and compute free energy surfaces. We found that, in spite of the strong hydrogen bonds anchoring water molecules in the tetrahedral cavity, the energy barrier for water release is lower than that for the chemical formation of water molecules from the hydroxyl groups. We then conclude that water release is not the rate-limiting step of the dehydration mechanism.