Optical Properties of Intermetallic Superalloys: An Investigation from Experiment and Theory

We present a combined experimental and theoretical investigation for the optical properties of Ni-based intermetallic superalloys. Using broadband infrared reflectivity and visible-light ellipsometry, we measure the complex frequency-dependent dielectric function and compare it with our findings from density functional based methods. The Ni-based intermetallic superalloy is modeled for various compositions (Ni60Cr25Fe15, Ni75Cr25, Ni) with a randomly distributed face-centered cubic supercell to explore the frequency-dependent dielectric function from the associated intra and interband transitions. We find reasonable agreement between theory and experiment regarding especially the distribution of spectral weight across the energy range <6eV for the superalloy composition which best represents the composition of the sample measured in the experiment. The striking similarities of the modeled and measured Ni60Cr25Fe15 optical functions indicate that complex, disordered systems can be understood using a simple computational scheme.