Study of the structural, electronic, optical and elastic properties of NaSrX3 (X = F, Cl) perovskite materials using the ab-initio method

In this work, we studied the structural, electronic, optical, and elastic properties of NaSrX₃ type perovskites (X: halogen F and Cl) using density functional theory (DFT) implemented in Quantum-expresso by GGA. The lattice parameters of NaSrF₃ and NaSrCl₃ are 4.01 Å and 4.65 Å, respectively. We discovered that NaSrF₃ behaves as an insulator, while NaSrCl₃ behaves as a semiconductor. They have direct gaps. The gap for NaSrF₃ is 6.02 eV and that for NaSrCl₃ is 4.09 eV. They all have a conduction band dominated by Sr 3d states, weakly mixed with Na 3s and Sr 4s states. The valence band is dominated by alkali 2p and Sr 3d states. These perovskites also have very good optical properties: low reflectivity and high absorption in the ultraviolet range. These materials are elastically stable. They have good rigidity and show greater resistance to bond bending and bond angle distortion. However, NaSrF₃ is ductile and NaSrCl₃ is brittle. NaSrCl₃ will withstand higher temperatures than NaSrF₃. This study shows that these materials are suitable for various applications in both the visible and UV ranges. They have very interesting properties for optoelectronics.