First-principles supercell calculations of small polarons with proper account for long-range polarization effects

Kokott, Sebastian; Levchenko, Sergey V.; Rinke, Patrick; Scheffler, Matthias

doi:10.1088/1367-2630/aaaf44

Cited by 56 publications

(61 citation statements)

References 48 publications

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“…However, hybrid functionals remain unsatisfactory because they contain undetermined parameters, such as the amount of incorporated Fock exchange. To overcome this deficiency, two different nonempirical determination schemes are being investigated at present, namely, * thomas.bischoff@epfl.ch dielectric-dependent hybrid (DDH) functionals [22][23][24][25][26][27][28][29][30][31][32] and hybrid functionals enforcing Koopmans' condition [33][34][35][36][37][38][39][40]. Both approaches exhibit great potential due to their promising combination of accuracy and computational cost.…”

Section: Introductionmentioning

confidence: 99%

Nonempirical hybrid functionals for band gaps of inorganic metal-halide perovskites

Bischoff

Wiktor

Chen

et al. 2019

Phys. Rev. Materials

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Nonempirical hybrid functionals are investigated for band-gap predictions of inorganic metal-halide perovskites belonging to the class CsBX 3 , with B = Ge, Sn, Pb and X = Cl, Br, I. We consider both global and range-separated hybrid functionals and determine the parameters through two different schemes. The first scheme is based on the static screening response of the material and thus yields dielectric-dependent hybrid functionals. The second scheme defines the hybrid functionals through the enforcement of Koopmans' condition for localized defect states. We also carry out quasiparticle self-consistent GW calculations with vertex corrections to establish state-of-the-art references. For the investigated class of materials, dielectric-dependent functionals and those fulfilling Koopmans' condition yield band gaps of comparable accuracy (∼0.2 eV), but the former only require calculations for the primitive unit cell and are less subject to the specifics of the material.

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Section: Introductionmentioning

confidence: 99%

Nonempirical hybrid functionals for band gaps of inorganic metal-halide perovskites

Bischoff

Wiktor

Chen

et al. 2019

Phys. Rev. Materials

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“…(1) includes both electronic and ionic contributions under relaxed atomic positions, we need a model or an assumption to estimate the respective alignment-like terms of the electronic and ionic parts, separately. In the cases of small polarons, one can estimate ∆V PC,q/b | far of the electronic part from the charge distribution using squared wavefunctions of localized polaronic states, as has been reported by Kokott et al [16], but such a method is not generally applicable to defects involving the removal and/or insertion of atoms. (a) (b) Number of atoms, N Number of atoms, N N -1/3 N -1/3 Relative energy (eV) -2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 0 0.1 0.2 0.3 1 0 0 0 5 1 2 2 1 6 6 4 -1.5 -1 -0.5 0 0.5 1 1.5 2 0 0.1 0.2 0.3 1 0 0 0 5 1 2 2 1 6 6 4 PC uncor w/o ε ion PC cor SO FIG.…”

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confidence: 99%

Finite-size corrections for defect-involving vertical transitions in supercell calculations

et al. 2020

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A correction method for vertical transition levels (VTLs) involving defect states calculated with a supercell technique is formulated and its effectiveness is systematically verified with 10 defects in prototypical materials: MgO, GaN, cubic-BN, and 3C-SiC. Within point-charge approximations, the corrected VTLs for cation vacancies are found to well reproduce their dilute limits, while they do not work as satisfactorily for anion vacancies. In contrast, when the finite defect size contribution is incorporated, the mean absolute errors are reduced and become less than 0.1 eV with moderate size supercells in all cases. Our correction scheme is a powerful technique because it is adaptive for evaluating various quantities at fixed geometry, as represented by those relevant to the generalized Koopmans' theorem.Point defects determine various physical properties in solids. One of the most important properties is the optical property. For instance, ZnO is known to show green luminescence, which is seemingly attributed to point defects [1]. Another example is SrTiO 3 , known to show blue-light emission at room temperature after Ar + -irradiation, whose origin is presumably the emergence of oxygen vacancies [2]. In addition, we can investigate defects with deep states, which often degrade the device performance, from the photo-absorption and -emission spectra. It is generally considered that absorption (emission) of a photon by a defect promotes (demotes) an electron to the excited (ground) state, most probably without altering the atomic configuration, based on the Franck-Condon principle [3]. This is a consequence of the fact that electrons are much lighter than nuclei. Thus, we can represent the optical transition by a vertical arrow in the configuration coordination diagram, and its transition energy is given as an optical transition level or vertical transition level (VTL) with respect to the valence band maximum (VBM) or the conduction band minimum (CBM) [4,5].First-principles calculations have become powerful tools to understand and predict the defect-mediated optical transitions. In the calculations of extended systems with defects, these levels are almost always evaluated by a supercell approach nowadays, where a charged defect interacts with its periodic images and background charge, which erroneously modifies the total energies of charged defect supercells [6,7]. Methods to correct the energies to the dilute limit are well established, as represented by the scheme proposed by Freysoldt, Neugebauer, and Van de Walle (FNV) [8], and its extension to anisotropic systems and/or relaxed geometries (eFNV) [9]. The correction energy of the eFNV scheme is written aswhere E PC is the point charge (PC) correction energy, * kumagai@msl.titech.ac.jp ∆V PC,q/b | far is the potential difference between defect-induced and PC potentials at a region outside of the defect in the supercell, and q is the defect charge state. The second term is referred to as an alignment-like term, and is approximately equal to the Makov-Payne thir...

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“…Moreover, the restrictiveness of the constraints can be decreased further on subsequent calculations until the desired level of accuracy is achieved. Figure 6 illustrates the uncorrected polaron energy for the free and constrained relaxation trajectories for these supercells [66]. Because charge localization is necessary when studying polarons, the HSE 2006 functional is used with a screening parameter of 0.11 Bohr −1 with exact exchange.…”

Section: Systems With Local Symmetries or Distortionsmentioning

confidence: 99%

Parametrically constrained geometry relaxations for high-throughput materials science

et al. 2019

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Reducing parameter spaces via exploiting symmetries has greatly accelerated and increased the quality of electronic-structure calculations. Unfortunately, many of the traditional methods fail when the global crystal symmetry is broken, even when the distortion is only a slight perturbation (e.g. Jahn-Teller like distortions). Here we introduce a flexible and generalizable parametric relaxation scheme, and implement it in the all-electron code FHI-aims. This approach utilizes parametric constraints to maintain symmetry at any level. After demonstrating the method's ability to relax metastable structures, we highlight its adaptability and performance over a test set of 359 materials, across thirteen lattice prototypes. Finally we show how these constraints can reduce the number of steps needed to relax local lattice distortions by an order of magnitude. The flexibility of these constraints enables a significant acceleration of the high-throughput searches for novel materials for numerous applications.

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First-principles supercell calculations of small polarons with proper account for long-range polarization effects

Cited by 56 publications

References 48 publications

Nonempirical hybrid functionals for band gaps of inorganic metal-halide perovskites

Nonempirical hybrid functionals for band gaps of inorganic metal-halide perovskites

Finite-size corrections for defect-involving vertical transitions in supercell calculations

Parametrically constrained geometry relaxations for high-throughput materials science

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