Insights into polarized Raman, infrared, and dielectric spectra of lead-free (Na _0.5 Bi _0.5 )ZrO ₃ : a density functional theoretical investigation

In this work, we present a DFT-based first-principles theoretical investigation of the lattice dynamics, electronic structure, and dielectric properties of the room-temperature phase of the Na_0.5Bi_0.5ZrO₃ (NBZ) system. In particular, theoretical and experimental Raman studies of the system are performed, and the symmetry labels of the NBZ vibrational modes are assigned. In addition, theoretical polarized Raman spectra, Born-effective charge tensors, infrared (IR) reflectivity, and oscillator strengths are obtained and analysed. The experimental bandgap energy is obtained using UV-vis spectroscopy. The experimental Raman spectra at room temperature are recorded. The experimental and computed Raman spectra show good agreement with each other. The Raman mode intensities are computed for different light polarization configurations, suggesting the presence of different symmetry modes for each polarization setup. The electronic band structure and density of states of NBZ are investigated, and the optical absorption spectrum is also determined. Moreover, we explored the effectiveness of DFT semi-local and hybrid and meta-GGA exchange correlation (XC) functionals and the impact of spin-orbit coupling (SOC) on electronic band gap estimations. The electron localization function, COHPs and Bader charge analysis are also carried out to determine the bonding nature in the NBZ compound. In summary, our work presents important benchmark insights into NBZ that have been not reported yet.