Universal temperature-dependent electrical resistivity in actinides

Abstract

Temperature-dependent electrical resistivity $ρ(T)$ is one of the most common types of experimental data analyzed in condensed matter physics. For one group of pure metals, the actinides, experimental $ρ(T)$ curves differ radically from one another to the point that there is no unified theoretical approach to understanding and fitting $ρ(T)$ data in these elements. First-principles calculations result in $ρ(T)$ curves that differ from experimental data, even qualitatively. In an attempt to unravel this long-standing problem, here I propose a simple model that accurately fits the $ρ(T)$ data for nine phases of elemental actinides (from thorium (Th) to curium (Cm)) for which experimental data are publicly available to date. The model is based on the concept of two parallel conduction channels: one is described by the Bloch-Grüneisen equation, which is associated with the classical electron-phonon dissipation mechanism, and the other by the Arrhenius equation, which is associated with the nearest-neighbor hopping (NNH) conductivity. Debye temperatures $Θ_D$ obtained by applying the model to the $ρ(T)$ data for nine elemental actinide phases are in good agreement with published values deduced from heat capacity measurements. For neptunium (Np) a maximum Arrhenius activation energy (among all actinides) of $E_a=15.9$ $meV$ was derived. The model was also successfully applied to $ρ(T)$ data measured on $δ$-phase plutonium-based alloys Pu-Ce and Pu-Ce-Ga.