Band structure calculations of CuAlO2, CuGaO2, CuInO2, and CuCrO

Roland Gillen

¹

,

John Robertson

²

Abstract

We report density functional theory (DFT) band structure calculations on the transparent conducting oxides CuAlO2, CuGaO2, CuInO2 and CuCrO2. The use of the hybrid functional sX-LDA leads to considerably improved electronic properties compared to standard local density approximation (LDA) and generalized gradient approximation (GGA) approaches. We show that the resulting electronic band gaps compare well with experimental values and previous quasiparticle calculations and show the correct trends with respect to the atomic number of the cation (Al, Ga, In). The resulting energetic depths of Cu d and O p levels and the valence band widths are considerable improvements compared to LDA and GGA and in good agreement with available x-ray photoelectron spectroscopy (XPS) data. Lastly, we show the calculated imaginary part of the dielectric function for all four systems.

Accurate screened exchange band structures for the transition metal monoxides MnO, FeO, CoO and NiO

“…We note that the strong shift of unfilled semi-core states compared to HSE03 and HSE06 is a known behaviour of sX-LDA 29,54 and is likely caused by the different inclusion of non-local exchange. While both functional types are conceptually similar in the sense that they employ a range separation scheme to screen the non-local exchange and generally yield similar band gaps, sX-LDA uses 100% of Thomas-Fermi screened HartreeFock exchange, whereas HSE only incorporates only 25% Hartree-Fock exchange, but with Error function screening and a weaker screening length compared to sX-LDA.…”

“…On the other hand, the typically stronger screening of the non-local exchange contribution in sX-LDA compared to HSE often leads to a weaker shift of the itinerant states in the conduction band, e.g. the "4s" states in case of the transition metal monooxides shown in this work, the Cu p states in copper-based transparent conducting oxides 54 , or the antibonding sp 3 states in silicon.…”

Nature of the electronic band gap in lanthanide oxides

“…3(b) that, as in CeO 2 , sX-LDA generally places the empty f levels at significantly higher energies than HSE (and G 0 W 0 @LDA+U ); they are always within the bulk conduction band for the first half of the lanthanide series, except for Eu 2 We note that the stronger energetic splitting of occupied and unoccupied semicore states compared to HSE03 and HSE06 is a known behavior of sX-LDA. 23,33 While both functional types are conceptually similar in the sense that they both screen the included nonlocal exchange component in a range-separation scheme, sX-LDA incorporates 100% of Thomas-Fermi screened Hartree-Fock exchange, whereas HSE includes only 25% Hartree-Fock exchange, but with a weaker error function screening and a larger screening length compared to sX-LDA. The very strong contribution of shortrange Hartree-Fock exchange within sX-LDA particularly affects more localized orbitals, such as the 4f states in the present lanthanide oxides, and leads to a stronger shift of the corresponding energy levels.…”

“…This gives a great improvement in the predicted electronic and magnetic properties. [14][15][16][17][18][19][20][21][22][23] Crucially, they are generalized KohnSham functionals 15 that allow a self-consistent calculation of ground-state properties giving a well defined total energy leading to atomic forces and geometries, in contrast to G 0 W 0 . We shall see that the different incorporation of nonlocal exchange into standard local functionals leads to interesting variations in the predicted band structures of the 15 Ln 2 O 3 oxides and of CeO 2 .…”

Sn(II)-Containing Phosphates as Optoelectronic Materials

“…SrCu 2 O 2 , with m * =2.1 m 0 and ZnRh 2 O 4 , with m * =3.4 m 0 . [4,5]. SnO, which has a band gap somewhat to small to be a good TCO in the visible, has a hole density of states effective mass m * =0.9 m 0 .…”