Publications (3)3.99 Total impact
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Article: Density-functional theory studies of pyrite FeS2 (111) and (210) surfaces
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ABSTRACT: We have performed DFT calculations using both plane wave-pseudopotential and Gaussian basis set approaches on the (1 1 1) and (2 1 0) surfaces of pyrite (FeS2). Our calculations indicate that the (1 1 1) surface is more stable than the (2 1 0) surface, which is predicted to have a higher surface energy. The (2 1 0) surface is predicted to be essentially bulk terminated, with a relatively small amount of surface relaxation. Bridging S atoms on the (1 1 1) surface undergo significant lateral displacement to coordinate to neighbouring undercoordinated surface Fe atoms. Electrostatic effects induced by loss of coordination at surface Fe atoms are likely to be responsible for surface ionic displacements. Our calculations indicate that surface Fe states dominate at the Fermi level on the (2 1 0) surface, but that surface S states make significant contributions to the valence band on the (1 1 1) surface. On the (2 1 0) surface, Fe atoms of 4-fold coordination are spin polarized and therefore paramagnetic, while 5-fold coordinated Fe are diamagnetic. For the (1 1 1) surface, both 5- and 6-fold coordinated Fe atoms are predicted to be spin polarized, although nominally the unpaired electrons are expected to be localised on the surface S− species. This is likely to be due to the removal of spin polarization from the surface S by charge transfer from the surface Fe.Surface Science 11/2002; 520:111-119. · 1.99 Impact Factor -
Article: Density-functional theory studies of pyrite FeS2(100) and (110) surfaces
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ABSTRACT: We have performed density-functional theory calculations using both plane wave-pseudopotential and Gaussian basis set approaches on the (1 0 0), planar (1 1 0) and microfacetted (1 1 0) surfaces of pyrite (FeS2). Our calculations indicate that the (1 0 0) surface is more stable than the planar (1 1 0) surface, which is predicted to have a higher surface energy. Creation of microfacets on the (1 1 0) surface resulted in a lower surface energy. Relatively small differences in calculated surface energy between the ideal and relaxed (1 0 0) and (1 1 0) surfaces were found. The (1 0 0) and (1 1 0) surfaces are predicted to be essentially bulk-terminated, with a relatively small amount of relaxation. Electrostatic effects induced by loss of coordination at surface Fe atoms are likely to be responsible for surface ionic displacements. Our calculations indicate that surface Fe atoms of fourfold coordination, present on the (1 1 0) surfaces, are spin polarized, while those of fivefold coordination are fully spin-paired. These results suggest that magnetic species, such as O2, are more prone to react at low Fe coordination defect sites on real FeS2 (1 0 0) surfaces.Surface Science 08/2002; 513(3):511-524. · 1.99 Impact Factor -
Article: First-principles studies of the structural and electronic properties of pyrite FeS_ {2}
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ABSTRACT: We present a study of the structural and electronic properties of Pyrite FeS2 performed using both localized basis set and plane wave first-principles calculations. Calculations performed using either Gaussian or plane wave basis sets yield results consistent with each other. Small differences in the computed geometries are shown to be due to the choice of pseudopotential employed in the plane wave calculations. The computed densities of states are relatively insensitive to the form of basis set and pseudopotential used. We find that density functional and hybrid approaches predict properties such as geometry and densities of states in good agreement with experiment but that the agreement between the results from Hartree–Fock (HF) calculations and experiment is poor. The reasons for the poor performance of HF theory in this system are examined and are found to be due to the neglect of electronic correlation.Phys. Rev. B. 65(5).
