Improved predictions of the physical properties of Zn- and Cd-based wide band-gap semiconductors: A validation of the ACBN0 functional

We study the physical properties of ZnX (X = O, S, Se, Te) and CdX (X = O, S, Se, Te) in the zinc-blende, rock-salt, and wurtzite structures using the recently developed fully ab initio pseudohybrid Hubbard density functional ACBN0. We find that both the electronic and vibrational properties of these wide band-gap semiconductors are systematically improved over the PBE values and reproduce closely the experimental measurements. Similar accuracy is found for the structural parameters, especially the bulk modulus. ACBN0 results compare well with hybrid functional calculations at a fraction of the computational cost.

Figure 1

Lower panel: Energy-volume curve of CdO in the rs phase as calculated by the ACBN0 functional. Upper panel: Variation of the converged $U_{\mathrm{eff}}$ of Cd and O in CdO as a function of lattice constant.

Figure 2

Comparison of percentage relative error in the predictions of (a) lattice constants, (b) bulk moduli, (c) band gap, and (d) energies of the $d$ band calculated using PBE, HSE, and ACBN0 functionals. All the absolute values are listed in Tables 3, 4, 5. The errors are calculated relative to the experimental values in Tables 3–5. In cases where there is more than one experimental value, we take the average of the minimum and the maximum value as the reference experimental value. Comparison is made only for the stable phases of the II-VI compounds. Black circles are the PBE values, open red squares are the HSE values, and open blue diamonds are the ACBN0 values. The experimental values are referenced by the black solid line at 0.

Figure 3

Band structure of $\mathrm{Zn}X$ ($X$ = O, S, Se, Te) within the ACBN0 (red lines) method for the stable wz and zb phase. The PBE (black lines) band structure is also shown for comparison. Brillouin zone integration follows the AFLOW standard as discussed in Ref. [63].

Figure 4

Band structure of $\mathrm{Cd}X$ ($X$ = O, S, Se, Te) within the ACBN0 (red lines) method for the stable rs and zb phase. The PBE (black lines) band structure is also shown for comparison. Brillouin zone integration follows the AFLOW standard as discussed in Ref. [63].

Figure 5

Phonon dispersion of $\mathrm{Zn}X$ ($X$ = S, Se, Te) within the ACBN0 method for the zb phase (red). The PBE phonon dispersions (black) is also shown for comparison. Open blue diamonds represent inelastic scattering data from Refs. [64, 65]. We show only the directions in the Brillouin zone that have been measured, see the Supplemental Material [32] for the full phonon dispersions.

Figure 6

Calculated phonon dispersion of $\mathrm{Cd}X$ ($X$ = O, S, Te) within the ACBN0 (red lines) and PBE (black lines) method for the zb phase. Open blue diamonds represent experiment inelastic neutron scattering data are from Refs. [66, 67]. We show only the directions in the Brillouin zone that have been measured, see the Supplemental Material [32] for the full phonon dispersions.