Comparison study of crystal and electronic structures for chalcopyrite (CuFeS2) and pyrite (FeS2)

Abstract

Chalcopyrite (CuFeS2) and pyrite (FeS2) are commonly associated with each other, and they both belong to semiconductor minerals. The difference in crystal and electronic structures is an important factor for their flotation separation. Using the density functional method (DFT) combined with Hubbard U correction, their crystal and electronic properties are comparatively studied. The calculated results suggest that the use of antiferromagnetic calculations and Hubbard U correction are very important to the accuracy of the chalcopyrite results. Antiferromagnetic calculations combined with a U value of 2.0 eV on chalcopyrite show a band gap of 0.53 eV, which is very consistent with the experimental results of ~0.5 eV. The density of states (DOS) and Mulliken bond population results indicate that stronger hybridization between Fe 3d and S 3p states in chalcopyrite than in pyrite leads to a stronger covalency of Fe-S bonds in chalcopyrite, causing a reduction in the spin magnetic moment (3.5 µB) from the ideal value. In addition, the greater covalency of bonds in chalcopyrite results in greater hydrophobicity of chalcopyrite than pyrite. The DOS results suggest that S has similar electronic properties in pyrite and chalcopyrite. The oxidation states of Fe and Cu ions in chalcopyrite are discussed based on the coordination field theory according to the calculation results, which confirms an oxidation state of Fe 3+ Cu 1+ S2.

The Effects of Chloride on the High Temperature Pressure Oxidation of Chalcopyrite: Some Insights from Batch Tests—Part 2: Leach Residue Mineralogy

“…As part of the reaction mechanism involved here, it is expected that dissolved Cu(I) would be rapidly oxidised by Fe(III), e.g., [60,61]. This is also consistent with the conclusion of Pearce et al [62] and the recent study of Li et al [63] that the oxidation states of copper and iron in chalcopyrite are +1 and +3, respectively; a survey of this and other related studies by Conejeros et al [64] suggests there is still controversy on this point.…”

First-Principles Study of Hg0 Immobilization on a Defective Pyrite Surface

“…The Monkhorst–Pack 6 × 6 × 6 and 3 × 3 × 1 meshes of k-points were used in the integration of the Brillouin zone for bulk and surface calculations, respectively. To further describe local electrons of Fe 3d orbitals, the Hubbard U correction ( U eff = 2 eV) was performed. ,− Spin polarization was also considered in all calculations. The self-consistent field (SCF) convergence tolerance of 1.0 × 10 –6 eV/atom was employed.…”

Tailoring Fe0 Nanoparticles via Lattice Engineering for Environmental Remediation

“…Different electrical conductivity and hydrophobicity of nFe 0 materials can be obtained by changing the speciation (e.g., FeS, FeS 2 , and CuFeS 2 ), resulting in a disparity in their reactivity and selectivity (Figure 4). 91,92 Coordination numbers that are affected by the valence states of Fe atoms and their coordination composition also need to be focused on. FeS x phases with different Fe coordination numbers also control the material's electron transfer and hydrophobicity; 43 e.g., polysulfides (e.g., Fe 3 S 4 = 0.0 eV) have lower band gap and faster electron transfer than other iron sulfides (e.g., FeS = 0.10 eV, FeS 2 = 0.95 eV).…”

“…Different electrical conductivity and hydrophobicity of nFe 0 materials can be obtained by changing the speciation (e.g., FeS, FeS 2 , and CuFeS 2 ), resulting in a disparity in their reactivity and selectivity (Figure ). , …”