A DFT study on cubic NaInBr₃ perovskite: insights into structural stability, electronic behavior, and optical performance

This work presents a first-principles investigation of cubic NaInBr₃ perovskite using density functional theory (DFT) within the generalized gradient approximation (GGA). The Structural optimization of the perovskite confirms its mechanical stability, yielding a lattice constant of 5.75 Å and a bulk modulus of 18.41 GPa, indicating that the compound is mechanically soft. The electronic band structure reveals a direct band gap of ~0.4 eV at the R point, highlighting its semiconducting nature and potential for optoelectronic applications. The density of states (DOS) shows dominant contributions from Br-4p and In-5p orbitals in the valence and conduction bands, respectively. Optical property calculations indicate a moderate static dielectric constant (ε₁ (0) = 3.53), a high absorption coefficient (1.32 × 10⁸ cm⁻¹), and pronounced plasmonic responses, suggesting potential applications in ultraviolet photodetectors, photovoltaics, and plasmonic devices. Thermodynamic analysis demonstrates structural and thermal stability across a broad pressure range, as evidenced by increasing Debye temperature, entropy, and specific heats, along with decreasing Gibbs and vibrational free energies. The obtained results of the study establish NaInBr₃ as a promising candidate for thermoelectric, ultraviolet optoelectronic, and high-temperature energy applications.