Electronic Structure Computations and Optical Spectroscopy Studies of ScNiBi and YNiBi Compounds

The work presents the electronic structure computations and optical spectroscopy studies of half-Heusler ScNiBi and YNiBi compounds. Our first-principles computations of the electronic structures were based on density functional theory accounting for spin-orbit coupling. These compounds are computed to be semiconductors. The calculated gap values make ScNiBi and YNiBi valid for thermoelectric and optoelectronic applications and as selective filters. In ScNiBi and YNiBi, an intense peak at the energy of −2 eV is composed of the Ni 3d states in the conduction band, and the valence band mostly contains these states with some contributions from the Bi 6p and Sc 3d or Y 4d electronic states. These states participate in the formation of the indirect gap of 0.16 eV (ScNiBi) and 0.18 eV (YNiBi). Within the spectral ellipsometry technique in the interval 0.22–15 μm of wavelength, the optical functions of materials are studied, and their dispersion features are revealed. A good matching of the experimental and modeled optical conductivity spectra allowed us to analyze orbital contributions. The abnormally low optical absorption observed in the low-energy region of the spectrum is referred to as the results of band calculations indicating a small density of electronic states near the Fermi energy of these complex materials.