Minerals 2014, 4(1), 89-115; doi:10.3390/min4010089

A Density Functional Theory Study of the Adsorption of Benzene on Hematite (α-Fe2O3) Surfaces

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Received: 13 December 2013; in revised form: 20 January 2014 / Accepted: 31 January 2014 / Published: 14 February 2014
(This article belongs to the Special Issue Advances in Low-temperature Computational Mineralogy)
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Abstract: The reactivity of mineral surfaces in the fundamental processes of adsorption, dissolution or growth, and electron transfer is directly tied to their atomic structure. However, unraveling the relationship between the atomic surface structure and other physical and chemical properties of complex metal oxides is challenging due to the mixed ionic and covalent bonding that can occur in these minerals. Nonetheless, with the rapid increase in computer processing speed and memory, computer simulations using different theoretical techniques can now probe the nature of matter at both the atomic and sub-atomic levels and are rapidly becoming an effective and quantitatively accurate method for successfully predicting structures, properties and processes occurring at mineral surfaces. In this study, we have used Density Functional Theory calculations to study the adsorption of benzene on hematite (α-Fe2O3) surfaces. The strong electron correlation effects of the Fe 3d-electrons in α-Fe2O3 were described by a Hubbard-type on-site Coulomb repulsion (the DFT+U approach), which was found to provide an accurate description of the electronic and magnetic properties of hematite. For the adsorption of benzene on the hematite surfaces, we show that the adsorption geometries parallel to the surface are energetically more stable than the vertical ones. The benzene molecule interacts with the hematite surfaces through π-bonding in the parallel adsorption geometries and through weak hydrogen bonds in the vertical geometries. Van der Waals interactions are found to play a significant role in stabilizing the absorbed benzene molecule. Analyses of the electronic structures reveal that upon benzene adsorption, the conduction band edge of the surface atoms is shifted towards the valence bands, thereby considerably reducing the band gap and the magnetic moments of the surface Fe atoms.
Keywords: hematite (α-Fe2O3); surfaces; benzene; adsorption and density functional theory
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MDPI and ACS Style

Dzade, N.Y.; Roldan, A.; de Leeuw, N.H. A Density Functional Theory Study of the Adsorption of Benzene on Hematite (α-Fe2O3) Surfaces. Minerals 2014, 4, 89-115.

AMA Style

Dzade NY, Roldan A, de Leeuw NH. A Density Functional Theory Study of the Adsorption of Benzene on Hematite (α-Fe2O3) Surfaces. Minerals. 2014; 4(1):89-115.

Chicago/Turabian Style

Dzade, Nelson Y.; Roldan, Alberto; de Leeuw, Nora H. 2014. "A Density Functional Theory Study of the Adsorption of Benzene on Hematite (α-Fe2O3) Surfaces." Minerals 4, no. 1: 89-115.

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