Investigation with ab-initio method of structural, mechanical, electronic, and optical properties of La2NiMnO6 double perovskite compound at different temperatures

In this study, the structural, mechanical, electronic, and optical properties of the rhombohedral La₂NiMnO₆ (LNMO) double perovskite compound at different temperatures were investigated using the ab-initio method based on density functional theory (DFT). The spin-polarized generalized gradient approximation (GGA) was employed in the calculations. The lattice parameters obtained from structural optimization showed high agreement (less than 1,2% difference) with experimental values. Mechanical properties were determined through elastic constants calculated using the stress-strain relationship. The obtained elastic constants were found to satisfy the Born stability criteria for the rhombohedral structure. Electronic band structure calculations revealed that LNMO exhibits a half-metallic character in the spin-polarized state. Optical properties were analyzed by calculating the real and imaginary parts of the frequency-dependent dielectric function, along with other optical functions (refractive index, extinction coefficient, reflectivity, energy loss function).