First-Principles Studies Of Ionic And Electronic Transport In Palladium Hydride

The transport properties of palladium hydride/deuteride are investigated using state-of-the-art density functional computational tools. This aspect of loaded hydride is important in that the resistance-loading curve is often used as a diagnostic in experiments to estimate the loading ratio. Understanding transport provides other important insights into some features of the nuclear reaction mechanism. This research involves both ionic and electronic degrees of freedom. For the ionic part, the focus is on the charge state of hydrogen/deuteron, in both a static and a dynamic (hopping) situation. Experiments show that hydrogen hops as fractional-charged positive ion in Pd lattice [1,2] while previous band structure calculations [3-5] always gave a negatively charged H in the ground state. This discrepancy is addressed in the current research and some results are already published [6]. The collective motion of ions is studied in the phonon structure and electron-phonon coupling constant using a perturbation density functional theory. The electronic part focuses on the density of state and the Fermi surface, which when combined with the electron-phonon coupling constant, determine the temperature and the H/D loading dependant resistivity curves. Our numerical results [7] qualitatively match experimental trends. The possible connections between this transport theory/mechanism and the non-equilibrium conditions required for excess heat are discussed.