Electronic structure and optical properties of ${\mathrm{ThPd}}_3$ and ${\mathrm{UPd}}_3$

We present calculations of the electronic and optical properties of the actinide compounds ${\mathrm{ThPd}}_3$ and ${\mathrm{UPd}}_3$ using the state-of-the-art full-potential linearized augmented-plane-wave method as implemented in the WIEN97 code. Both compounds crystallize in the complex ${\mathrm{TiNi}}_3$ structure with 16 atoms per unit cell. For comparison with earlier work, we also studied these compounds in the ${\mathrm{AuCu}}_3$ structure. However, we find that the results in this hypothetical structure do not compare that well with experiments as in the actual ${\mathrm{TiNi}}_3$ structure. We have calculated the density of states (DOS), the coefficient of the electronic specific heat, and the frequency-dependent optical conductivity. These quantities are compared with experiments where good agreement is obtained. The DOS is dominated by $\mathrm{Pd}d$ states below the Fermi energy and by $\mathrm{actinide}f$ states near and above the Fermi energy. Transitions between these states dominate the optical conductivity and we find that the optical matrix elements do not play an important role. This finding is supported by experiments on a comparison of x-ray photoemission spectroscopy (XPS) data with optical conductivity.