Deciphering the Emerging Properties of the Multifunctional ZnO by LDA and GGA Approximations

The multifunctional Zinc oxide (ZnO) material is a wide-bandgap semiconductor with significant potential for optoelectronic, photovoltaic, and photonic applications. However, conventional density functional theory (DFT) approximations, such as the generalized gradient approximation (GGA) and the local density approximation (LDA), severely underestimate its bandgap, thereby limiting the accuracy of the predicted electronic and optical properties. In this work, a comprehensive theoretical investigation of wurtzite ZnO was carried out using the full-potential linearized augmented plane wave (FP-LAPW) method implemented in the WIEN2k code. The novelty of this study lies in a systematic comparative analysis of the structural, electronic, optical, and mechanical properties of ZnO calculated within the GGA and LDA frameworks, before and after the application of the TB-mBJ and TB-mBJ+SO corrections. The results reveal that the TB-mBJ and TB-mBJ+SO corrections have a negligible effect on the structural parameters while significantly improving the description of the electronic structure. The direct bandgap increases from 0.7686 eV (GGA) and 0.8290 eV (LDA) to 2.6512 eV and 2.7555 eV with the TB-mBJ potential, respectively, and then decreases slightly to 2.6241 eV and 2.7247 eV after the inclusion of spin-orbit coupling, confirming the weak influence of relativistic effects (Δ SO = 0.05356 eV). Consequently, the optical properties are described more realistically, while the calculated elastic constants satisfy the Born stability criteria. These findings demonstrate that the TB-mBJ correction significantly enhances the reliability of DFT calculations and represents an effective approach for accurately predicting the multifunctional properties of ZnO for advanced optoelectronic applications.