Specific features of the electronic structure and spectral properties of NdNi$_{5-x}$Cu$_x$ compounds

The spectral properties of the intermetallic compounds NdNi$_{5-x}$Cu$_x$ ($x$ = 0, 1, 2) have been studied using optical ellipsometry in the wavelength range 0.22–16 $\mu$m. It has been established that substitution of copper atoms for nickel leads to noticeable changes in the optical absorption spectra, plasma frequencies, and relaxation frequencies of conduction electrons. Spin-polarized calculations of the electronic structure of these compounds have been performed in the local spin density approximation allowing for strong electron correlations (LSDA + U method) in the 4f shell of the rare-earth ion. The calculated electron densities of states have been used to interpret the experimental dispersion curves of optical conductivity in the interband light absorption region.