Limitations of the DFT–1/2 method for covalent semiconductors and transition-metal oxides

Abstract

The DFT-1/2 method in density functional theory [L. G. Ferreira et al., Phys. Rev. B 78, 125116 (2008)] aims to provide accurate band gaps at the computational cost of semilocal calculations. The method has shown promise in a large number of cases, however some of its limitations or ambiguities on how to apply it to covalent semiconductors have been pointed out recently [K.-H. Xue et al., Comput. Mater. Science 153, 493 (2018)]. In this work, we investigate in detail some of the problems of the DFT-1/2 method with a focus on two classes of materials: covalently bonded semiconductors and transition-metal oxides. We argue for caution in the application of DFT-1/2 to these materials, and the condition to get an improved band gap is a spatial separation of the orbitals at the valence band maximum and conduction band minimum.

Surface electronic structure of bismuth oxychalcogenides

“…Such a dependence of the band structure on the Ch potential parameter does not allow us to apply the DFT-1/2 method confidently for Bi 2 O 2 Ch without knowledge of the experimental data or results of advanced band structure calculation methods. The limitations of the DFT-1/2 method for transition-metal oxides were also discussed recently [80]. On the other hand, the calculated DFT-1/2 bulk spectra are in close agreement with our mBJ (HSE06) and earlier GW calculation results, which makes this method applicable to surface band structure calculations in Bi 2 O 2 Ch compounds.…”

Band gap, effective masses, and energy level alignment of 2D and 3D halide perovskites and heterostructures using DFT-1/2

“…1/2e − or 1/4e − ) and different cutoff radii for the relevant orbitals were adopted to include the effect of the chemical environment. This further illustrates the intrinsic limitation and the semi-empirical character of the method as previously discussed 111 . Anyhow, DFT-1/2 correction assumes a priori knowledge of the orbitals composing the VBM, by virtue of which the full ab initio like picture is clearly lost.…”

Density Functional Theory Half-Electron Self-Energy Correction for Fast and Accurate Nonadiabatic Molecular Dynamics

“…Likewise, our calculations show that the HSE06 functional predicts a deep electron trap state induced by a phosphorus monovacancy in BP while PBE and PBE-1/2 lead to a shallow electron trap state (Figure S8), in agreement with previous work . As a consequence, it seems to be unlikely to produce correct electronic structures and quantum dynamics of covalent semiconductors and transition-metal oxides in the presence of defect-induced deep midgap states due to the intrinsic shortcomings of the DFT-1/2 method …”

“…71 As a consequence, it seems to be unlikely to produce correct electronic structures and quantum dynamics of covalent semiconductors and transition-metal oxides in the presence of defect-induced deep midgap states due to the intrinsic shortcomings of the DFT-1/2 method. 72 In summary, we demonstrated for the first time that DFT-1/ 2 electron self-energy correction can reproduce the excitedstate lifetimes at the hybrid functionals level while maintaining the computational cost at the semilocal PBE functional by investigating electron−hole recombination in rutile TiO 2 and a BP monolayer using NA-MD simulations. The calculated bandgap and effective masses of electrons and holes of TiO 2 and BP agree well between the PBE-1/2 and HSE06 methods, showing good agreement with experiment compared to those obtained using the PBE functional.…”