Adsorption of As(OH)3 on the (001) Surface of FeS2 Pyrite: A Quantum-mechanical DFT Study

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• 作者：Marc Blanchard ; Kate Wright ; Julian D. Gale ; C. Richard A. Catlow
• 刊名：Journal of Physical Chemistry C
• 出版年：2007
• 出版时间：August 2, 2007
• 年：2007
• 卷：111
• 期：30
• 页码：11390 - 11396
• 全文大小：241K
• 年卷期：v.111,no.30(August 2, 2007)
• ISSN：1932-7455

文摘

We have performed first-principles calculations based on density functional theory (DFT), to model interactionsof arsenic with FeS₂ pyrite. An understanding of pyrite reactivity on the atomic scale is needed to predict theavailability and mobility of arsenic in reducing conditions. Modeling of surface processes, however, requireslarge systems involving a vacuum part under periodic conditions, which makes plane-wave DFT methodsvery expensive computationally. We take advantage here of the use of localized pseudo-atomic orbitals asimplemented in the DFT code SIESTA to model bulk surface reactions of pyrite with arsenic. The lattermethod shows good agreement with the available data (theoretical and experimental) for the structure ofFeS₂ pyrite, the arsenic substitution in the bulk pyrite, as well as the energetics and relaxation of the (001)pyrite surface. This method has been employed to investigate the adsorption of As(OH)₃ on the (001) surfaceand the potential arsenic segregation with respect to the same surface. Our calculations suggest that the bestadsorption configuration is a bidentate complex with two Fe-O bonds, which is similar to the first surfacecomplexes observed in arsenite adsorption experiments. Once the arsenic atom is incorporated at the surfaceby substitution with a sulfur atom, it will readily incorporate into the bulk during pyrite growth; no segregationof arsenic with respect to the (001) pyrite surface is expected.