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Minerals 2015, 5(4), 665-678; https://doi.org/10.3390/min5040516

Ab initio Studies of O2 Adsorption on (110) Nickel-Rich Pentlandite (Fe4Ni5S8) Mineral Surface

Materials Modelling Centre, University of Limpopo, Private Bag X1106, Sovenga 0727, South Africa
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Academic Editor: Athanasios Godelitsas
Received: 9 June 2015 / Revised: 29 July 2015 / Accepted: 30 July 2015 / Published: 12 October 2015
(This article belongs to the Special Issue Mineral Surface Science and Nanogeoscience)
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Abstract

Ab initio density functional theory was used to investigate the adsorption of oxygen molecule on the nickel-rich pentlandite (110) surface, which is important for mineral extraction. The three most reactive adsorption sites: Fe-top, Ni-top, and fcc-hollow have been considered. Firstly, the non-adsorbed pentlandite surface reflects the Ni atoms relaxing inwards. Consequently, their electronic structure showed high Fe 3d-orbital contribution than the Ni 3d-orbitals at the EF (indicating that the Fe atoms are more reactive than Ni). Secondly, the O2-adsorbed surface predicted lowest adsorption energy for Fe-top (-1.902 eV), as a more spontaneous reaction is likely to occur than on fcc-hollow (-1.891 eV) and Ni-top (-0.040 eV) sites, suggesting Fe preferential oxidation. The density of states indicates that the O2 show prevalence of electrons in the πp* antibonding orbitals, and are reduced to zero states at the valence band on metal-bonded oxygen (O1). The πp* orbital is observed to reside just above the EF for Fe-top and fcc-hollow site, while on Ni-top is half-occupied for both metal-bonded oxygen (O1) and terminal oxygen (O2). Finally, the isosurface charge density difference showed electron (charge) depletion on Ni/Fe metals and accumulation on the O2 molecule. Bader analysis indicated that the oxidized Fe and Ni atoms adopt more positive charge, while O2 on Fe-top atoms possesses more negative charge than on Ni-top, resulting with O1 possessing a smaller charge than O2 atom. View Full-Text
Keywords: nickel-rich pentlandite (Fe4Ni5S8); (110) surface; oxidation; adsorption energies; density of states; Bader analysis; electronic properties; isosurface charge density nickel-rich pentlandite (Fe4Ni5S8); (110) surface; oxidation; adsorption energies; density of states; Bader analysis; electronic properties; isosurface charge density
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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. (CC BY 4.0).
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Mkhonto, P.P.; Chauke, H.R.; Ngoepe , P.E. Ab initio Studies of O2 Adsorption on (110) Nickel-Rich Pentlandite (Fe4Ni5S8) Mineral Surface. Minerals 2015, 5, 665-678.

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