Hybrid functionals and electronic structure of high‐pressure phase of CdO

Abstract

The electronic band structure and density of states (DOS) of B2-phase cadmium oxide (CdO) are computed following the firstprinciples linear combination of atomic orbitals method applying the CRYSTAL code. The PBE correlation functional coupled with Becke's ansatz for exchange is considered for calculations. The electronic band structure and DOS are examined considering HF, B3LYP and hybrid schemes. Hybrid functionals are used with 25, 15, 10 and 5% mixing of Fock exchange with PBE-GGA. Depending on the correlation functionals, and different mixings in the hybrid schemes, B2-phase CdO may have an indirect positive band gap, a negative band gap or a zero gap. The effect of pd repulsion originating from pd hybridisation is visible in the calculated band structures.

Optical properties of ZnSe using linear response theory

“…It is known that the XC functionals based on LDA and GGA do not correctly estimate the band gap within the DFT. For correct band gap other schemes like GW and more often hybrid functionals such as PBE0, HSE06 etc are used [50,51]. The f χ gc (q, ω) = 1 − χ S (q, ω) f (1) xc (q, ω)…”

Thermoelectric and vibrational properties of Be2C, BeMgC and Mg2C using first-principles method

“…Usage of hybrid functional brings the band gap values close to the many body GW calculations which are believed to give accurate band gap in semiconductors. [19][20][21] Better agreement of band gap from quasi particle or GW calculations with the hybrid functional and also with experiments, in some cases, is ascribed to the fact that hybrid functionals essentially augment LDA or GGA by non-local exchange. [19][20][21] The underestimation of band gap by DFT has commonly been attributed to the inappropriate treatment of the XC functional [20][21][22]52 and the incomplete cancellation of the articial self-interaction 20,52 within the LDA (local) or GGA (semi-local) descriptions.…”

“…[19][20][21] Better agreement of band gap from quasi particle or GW calculations with the hybrid functional and also with experiments, in some cases, is ascribed to the fact that hybrid functionals essentially augment LDA or GGA by non-local exchange. [19][20][21] The underestimation of band gap by DFT has commonly been attributed to the inappropriate treatment of the XC functional [20][21][22]52 and the incomplete cancellation of the articial self-interaction 20,52 within the LDA (local) or GGA (semi-local) descriptions. The hybrid functional, generally, combines the 1 4 non-local exchange, 3 4 of the semi-local exchange with the correlation functional.…”

“…18 Recent trends are to use hybrid functionals to get accurate values of the band gap and bands dispersion which works well in some solids. [19][20][21][22] The hybrid functionals club merit of both approaches. Many methods use a number of hybrid functionals from the library of exchange and correlation (XC) functionals.…”

First-principles characterisation of structural and electronic properties of some RuO2 crystals

“…For instance, the ground state of some oxides is not correctly predicted. The LDA and GGA systematically underestimate the bandgap in semiconductors and insulators compared to the experiments [29][30][31]. The approximate exchange and correlation (XC) functionals are inadequate to capture the physics of interacting d electrons.…”