DFT Research on the Dehydroxylation Reaction of Pyrophyllite 1. First-Principle Molecular Dynamics Simulations

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• 作者：Esther Molina-Montes ; Davide Donadio ; Alfonso Herná ; ndez-Laguna ; C. Ignacio Sainz-Dí ; az ; Michele Parrinello
• 刊名：Journal of Physical Chemistry B
• 出版年：2008
• 出版时间：June 12, 2008
• 年：2008
• 卷：112
• 期：23
• 页码：7051 - 7060
• 全文大小：2323K
• 年卷期：v.112,no.23(June 12, 2008)
• ISSN：1520-5207

文摘

The dehydroxylation of pyrophyllite involves the reaction of OH groups and elimination of water molecules through two possible mechanisms, one involving the bridging hydroxyl groups of an octahedral Al³⁺ pair and the other two hydroxyl groups reacting across the dioctahedral vacancy. First-principles molecular dynamics simulations at the density functional theory level are used together with the metadynamics algorithm to explore the free-energy surface (FES) of the initial step of the dehydroxylation. We observe that the two possible dehydroxylation mechanisms yield similar activation energies at 0 K, but at high temperatures, the cross mechanism has lower free energy than that of the on-site one. The dehydroxylation process produces different semidehydroxylated intermediates that should be taken into account. The role of the temperature in favoring a dehydroxylation nonconcerted chain mechanism over another is here elucidated, and a novel competitive mechanism, which is assisted by the structural apical oxygens in the high-temperature regime, is proposed.