Study of optical and elastic properties of Fe3Se4 through DFT

Here in this work, the optical and elastic properties of Fe3Se4 were studied through the density functional theory (DFT) approach using the first-principles calculations. Independent–particle approximation method (IPA) is used to study the optical properties of Fe3Se4. The refractive index, electron energy loss spectrum, reflectivity, and absorption coefficient of Fe3Se4 were evaluated through optical properties. From the graph of the dielectric function, the dielectric constant of Fe3Se4 comes out to be very high which shows that Fe3Se4 behaves as a metallic material. Along with this, the elastic constant of Fe3Se4 was estimated by the stress–strain method. The elastic moduli of the triclinic structure were calculated by the Reuss-Voigt-Hill method. With the help of the 13 independent constants Cij, elastic properties like all the modulus B (Bulk), G (Shear), and E (Young’s) of Fe3Se4, along with Poisson’s ratio ν and anisotropy elastic AU, were determined. From B/G ratio calculations, it was concluded that Fe3Se4 behaves as a brittle material when no pressure is applied, and when a pressure of 20 GPa or higher than that is applied, it shows a ductile nature.