Systematic study of phase transformation, wide-to-narrow electronic band transition and optical properties of barium zirconium Oxynitrate: Ab initio calculations

Abstract

We report, for the first time, the structural phase transformation, wide-to-narrow electronic band transition and impact on optical properties, computed via ab initio methods by employing generalized gradient approximation of Perdew–Burke–Ernzerhof and ultra-soft pseudo-potential, with different nitrogen (N2) doping concentrations at oxygen (O2) lattice sites in BaZrO3. With an increase in N2 concentration, we observe an increase in the population of density of states with both energy bands and conduction band- moves towards the Fermi level. Consequently, a systematic reduction in the electronic band gap (from 3.119 to 1.152 eV) is observed due to prominent shifting of Zr d-states to lower conduction bands along with N2 and O2 p-states in upper valence bands, and also, its nature changes into the direct form. The mystery of decreasing band gap is nicely decoded by the total density of states and elemental partial density of states. Optical properties have also been computed to see the impact of decrement in band gap on them. The static refractive index is increased (from 2.196 to 2.988). The absorption edge is shifted to lower energy (from 1.6 to 0.02 eV, red shift). The optical properties confirm that the doped compound would be appropriate for absorbing electromagnetic radiations in the visible and IR regions of the electromagnetic spectrum as it has vast applications in optoelectronics.