Influence of hydrogen absorption on low-energy electronic collective excitations in palladium

Abstract

A theoretical study of electronic excitation spectra in Pd and PdH is reported. The calculations were performed with full inclusion of the electron band structure obtained within self-consistent pseudopotential approach. We demonstrate that the complicated Pd electronic structure at the Fermi level is reflected in a numerous peak structure of the excitation spectra. The evolution of the energy-loss spectrum with momentum and its anisotropy are analyzed. Strong modification of the excitation spectra upon hydrogen absorption is found. We also study the role of intra-and interband transitions in the formation of dominating plasmon peak both in pure Pd and PdH. In Pd, this peak is mainly determined by intraband transitions. The downward shift of this peak from ϳ7.2 eV in pure Pd to ϳ4.2 eV in PdH is mainly explained by interband transitions from occupied Pd d bands to unoccupied hydrogen-modified sp states in the 7 -13 eV energy range.

Warm Dense Matter Generation and DD Synthesis at Vacuum Discharge with Deuterium‐Loaded Pd Anode

“…The oscillation scales are being commensurable with the lattice parameter (typically, ∼ 0.3-0.4 nm). As a result, as authors supposed [20,37], the correspondent acceleration of D + could lead to enhance of DD-reaction yield even for a low energy deuteride excitation.…”

“…This is one of the number of models which are developing to explain the possible so-called low energy nuclear reactions (LENR) at deuterium-loaded Pd ( see review [36]). Recent theoretical study [37] and calculations [20] have shown that the excitation of the hydrogen subsystem (which leads to desorption of H,D) as a result of the electron bombardment is stipulated by the generation of plasma oscillations in the crystalline lattice, which are localized preferentially in the vicinity of hydrogen (deuterium) atoms. This process results in the electron-density oscillations and in the appearance of strong electric fields (∼ 10 8 V/cm) in the volume and on the plane of the hydride.…”

“…However, the available stage of study does not allow us to share properly the possible standard explosive evaporation of anode material by electron beam [7] (or any superheating effects under fast energy deposition [39]) from more exciting scenario of triggering any nuclear reactions on deuterium-loaded Pd anode surface by electron beams at the process of vacuum discharge. But if these kind of anode ectons do exist, in fact, their nature could be related with effects of electron beam -loaded Pd surface micro pores interactions at initial stage of discharge ("classical" physics like micro-scale system of IECF with multichannel microreactor at r V C → 0 [35], figs.17,18) or could be related with some LENR effects stimulated by electron beam (like discussed at [20,37,38]). The overlapping of both mechanisms is not excluded also, and have to be a subject of further study as well as analysis and verification of other mechanisms, like recently recognizing the opportunity of laser-driven (or beam-driven) microfusion in ultra-dense deuterium clusters as dislocation cores at host lattice [21,22].…”

Tuning the plasmon energy of palladium–hydrogen systems by varying the hydrogen concentration

“…The profile of Im[ϵ −1 ] is dominated by a broad feature whose energy smoothly shifts from ω P ≈ 7.7 eV for x = 0 to ω P ≈ 4.3 eV for x = 1. This peak is commonly attributed to the bulk plasmon although interband electron-hole pair transitions contribute to the weight as well [27]. Increasing the concentration of H in bulk PdH x shrinks the width of the plasmon peak and reduces its weight, due to the reduction in the density of states at the Fermi level and the increasing importance of interband electron-hole pair transitions.…”

“…Technical details of the first-principles calculations are similar to those used for Pd and PdH in Reference [27] and are only briefly summarized here. Density functional theory (DFT) is used to obtain the ground state of bulk PdH x for different values of x.…”