Abstract
The pyrite and marcasite polymorphs of FeS2 have attracted considerable interests for their potential applications in optoelectronic devices because of their appropriate electronic and optical properties. Controversies regarding their fundamental band gaps remain in both experimental and theoretical materials research of FeS2. In this work, we present a systematic theoretical investigation into the electronic band structures of the two polymorphs by using many-body perturbation theory with the GW approximation implemented in the full-potential linearized augmented plane waves (FP-LAPW) framework. By comparing the quasi-particle (QP) band structures computed with the conventional LAPW basis and the one extended by high-energy local orbitals (HLOs), denoted as LAPW + HLOs, we find that one-shot or partially self-consistent GW (G 0 W 0 and GW 0, respectively) on top of the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation with a converged LAPW + HLOs basis is able to remedy the artifact reported in the previous GW calculations, and leads to overall good agreement with experiment for the fundamental band gaps of the two polymorphs. Density of states calculated from G 0 W 0@PBE with the converged LAPW + HLOs basis agrees well with the energy distribution curves from photo-electron spectroscopy for pyrite. We have also investigated the performances of several hybrid functionals, which were previously shown to be able to predict band gaps of many insulating systems with accuracy close or comparable to GW. It is shown that the hybrid functionals considered in general fail badly to describe the band structures of FeS2 polymorphs. This work indicates that accurate prediction of electronic band structure of FeS2 poses a stringent test on state-of-the-art first-principles approaches, and the G 0 W 0 method based on semi-local approximation performs well for this difficult system if it is practiced with well-converged numerical accuracy.
Highlights
Iron disulfide FeS2 was studied extensively in the last century in the desire of understanding the structural and electronic properties of transition metal dichalcogenides (TMDC) featuring localized or band-like d electrons (Hulliger and Mooser, 1965a; Hulliger and Mooser, 1965b; Goodenough, 1972; Wilson, 1972; Li et al, 1974; Schlegel and Wachter, 1976; Folkerts et al, 1987)
With the all-electron many-body GW method implemented in the linearized augmented plane-wave (LAPW) framework, we find that by using GW0@PBE with the LAPW + high-energy local orbitals (HLOs) basis, pyrite and marcasite are predicted to have indirect fundamental band gaps of 1.14 and 1.16 eV, respectively
The pyrite band gap from GW0@PBE with LAPW + HLOs is very close to the generally accepted experimental value (Ennaoui et al, 1993) and the corresponding density of states agrees well with energy distribution curves obtained from the photoelectron spectroscopy measurements (Folkerts et al, 1987; Mamiya et al, 1997)
Summary
Iron disulfide FeS2 was studied extensively in the last century in the desire of understanding the structural and electronic properties of transition metal dichalcogenides (TMDC) featuring localized or band-like d electrons (Hulliger and Mooser, 1965a; Hulliger and Mooser, 1965b; Goodenough, 1972; Wilson, 1972; Li et al, 1974; Schlegel and Wachter, 1976; Folkerts et al, 1987). FeS2 Band Structure (Chatzitheodorou et al, 1986; Ennaoui et al, 1986), increasing practical interest has been drawn to pyrite FeS2 for its potential as a cheap and competitive candidate material for efficient solar energy conversion (Wadia et al, 2009) because of its natural abundance, non-toxicity, suitable optical gap and extraordinarily large absorption coefficient (Ferrer et al, 1990; Ennaoui et al, 1993) This has led to new solutions under various optoelectronic scenarios, including photovoltaics (Khalid et al, 2018), photocatalysis (Tian et al, 2015; Barawi et al, 2016), solid-state photocapacitors (Gong et al, 2013a) and photo-detectors (Wang et al, 2012; Gong et al, 2013b). We investigate the performances of several hybrid functionals, including PBE0 (Perdew et al, 1996b), HSE06 (Heyd et al, 2003, Heyd et al, 2006), screened-exchange-PBE hybrid functional (SX-PBE) (Bylander and Kleinman, 1990; Seidl et al, 1996) and DSH (Cui et al, 2018), in attempt to obtain insights into the failure of the conventional fixedparameter functionals in predicting the band gap of FeS2
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