Electronic structure of 3d pyrite- and marcasite-type sulphides

Bullett, D.W.

doi:10.1088/0022-3719/15/30/010

Cited by 176 publications

(81 citation statements)

References 41 publications

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“…Intuitively, one may reason that marcasite should have a lower gap than pyrite, because marcasite has lower symmetry compared to pyrite, and hence enhanced crystal field splitting. 27 Nonetheless, there is no direct, unambiguous evidence that marcasite has a lower gap than pyrite.…”

Section: Presence Of Marcasitementioning

confidence: 99%

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First-principles electronic structure and relative stability of pyrite and marcasite: Implications for photovoltaic performance

2011

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Despite the many advantages (e.g., suitable band gap, exceptional optical absorptivity, earth abundance) of pyrite as a photovoltaic material, its low open circuit voltage (OCV) has remained the biggest challenge preventing its use in practical devices. Two of the most widely-accepted reasons for the cause of the low OCV are: (i) Fermi level pinning due to intrinsic surface states that appear as gap states; (ii) the presence of the metastable polymorph, marcasite. In this paper, we investigate these claims, via density-functional theory (DFT), by examining the electronic structure, bulk, surface, and interfacial energies of pyrite and marcasite. Regardless of whether the Hubbard U correction is applied, the intrinsic {100} surface states are found to be of d z 2 character, as expected from ligand field theory. However, they are not gap states, but located at the conduction band edge. Thus, ligand field splitting at the symmetry-broken surface cannot be the sole cause of the low OCV. We also investigate epitaxial growth of marcasite on pyrite. Based on the surface, interfacial, and strain energies of pyrite and marcasite, we find from our model that only one layer of epitaxial growth of marcasite is thermodynamically favorable. Within all methods used (LDA, GGA-PBE, GGA-PBE+U , GGA-AM05, GGA-AM05+U , HSE06, ∆-sol), the marcasite Kohn-Sham gap is not less than the pyrite Kohn-Sham gap, and is even larger than the experimental marcasite gap. Moreover, gap states are not observed at the pyrite-marcasite interface. We conclude that intrinsic surface states or presence of marcasite is unlikely to undermine the photovoltaic performance of pyrite.

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Section: Presence Of Marcasitementioning

confidence: 99%

“…For example, the pyrite band structure calculated by linear combination of atomic orbitals (LCAO) can be found in Ref. 27; a DFT calculation is presented in Ref. 13.…”

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confidence: 99%

First-principles electronic structure and relative stability of pyrite and marcasite: Implications for photovoltaic performance

2011

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“…All can be subsumed by symmetry changes wrought by a structural phase transition 5 . The cubic pyrite crystal NiS 2 has long been recognized as a canonical Mott-Hubbard correlated insulator 2,[8][9][10][11][12][13] . Band structure calculations 11 put the sulfur 3p band and Ni t 2g band well below the half filled Ni e g band, pointing to on-site Coulomb repulsion as the source of the insulating energy gap E g , which lies in the range 1-10 meV (Ref.…”

Section: Introductionmentioning

confidence: 99%

Magnetism, structure, and charge correlation at a pressure-induced Mott-Hubbard insulator-metal transition

et al. 2011

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We use synchrotron x-ray diffraction and electrical transport under pressure to probe both the magnetism and the structure of single crystal NiS2 across its Mott-Hubbard transition. In the insulator, the low-temperature antiferromagnetic order results from superexchange among correlated electrons and couples to a (1/2, 1/2, 1/2) superlattice distortion. Applying pressure suppresses the insulating state, but enhances the magnetism as the superexchange increases with decreasing lattice constant. By comparing our results under pressure to previous studies of doped crystals we show that this dependence of the magnetism on the lattice constant is consistent for both band broadening and band filling. In the high pressure metallic phase the lattice symmetry is reduced from cubic to monoclinic, pointing to the primary influence of charge correlations at the transition. There exists a wide regime of phase separation that may be a general characteristic of correlated quantum matter.

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“…7 Although the band gap of ZnS 2 has not been experimentally determined, it is estimated to be 2.5 eV. 8 10,11 though their band gaps have not been evaluated. Elements that do not form the pyrite crystal structure with S can, in principle, also be used as alloying additions to FeS 2 , although in many cases their enthalpy of mixing is large.…”

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Feasibility of band gap engineering of pyrite FeS2

Sun

Ceder

2011

Phys. Rev. B

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We use first-principles computations to investigate whether the band gap of pyrite FeS2 can be increased by alloying in order to make it a more effective photovoltaic material. In addition to the isostructural compounds that have a larger band gap (ZnS2, RuS2, OsS2), we evaluate non-rareearth isovalent alloying candidates among all metals, transition metals, and semiconductor elements up to group IV and period 6 in the periodic table. From this screening procedure, we find that the group II elements (Be, Mg, Ca, Sr, Ba) and Cd have higher band gaps in the pyrite structure than FeS2. Practical band gap enhancement is observed only in the Ru and Os alloyed systems, but their incorporation into pyrite may be severely limited by the large positive enthalpy of mixing. All other candidate (Fe, M)S2 systems exhibit very large gap bowing effects such that the band gap at intermediate compositions is even lower than that of FeS2. Positive correlations between immiscibility and differences in electronegativity and Shannon ionic radius are observed.

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Electronic structure of 3d pyrite- and marcasite-type sulphides

Cited by 176 publications

References 41 publications

First-principles electronic structure and relative stability of pyrite and marcasite: Implications for photovoltaic performance

First-principles electronic structure and relative stability of pyrite and marcasite: Implications for photovoltaic performance

Magnetism, structure, and charge correlation at a pressure-induced Mott-Hubbard insulator-metal transition

Feasibility of band gap engineering of pyrite FeS2

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