Low-energy dielectric screening in Pd and PdHx systems

Area of Science:

• Condensed Matter Physics
• Materials Science
• Theoretical Chemistry

Background:

• Dielectric properties of palladium (Pd) are crucial for its applications.
• Understanding hydrogen's effect on Pd's electronic structure is key to material design.
• Previous work identified an acoustic-like plasmon (AP) in clean Pd.

Purpose of the Study:

• To theoretically investigate modifications in palladium's dielectric properties upon hydrogen absorption.
• To trace the evolution of the acoustic-like plasmon (AP) with increasing hydrogen concentration.
• To analyze changes in screening properties of palladium hydride (PdHx) systems.

Main Methods:

• Theoretical investigation using first-principles calculations.
• Full inclusion of electronic band structure via a self-consistent pseudopotential approach.
• Analysis of dielectric properties in the low-energy (0-2 eV) region.

Main Results:

• The acoustic-like plasmon (AP) exists in PdHx up to a specific hydrogen concentration (x) where 4d Pd-derived bands are completely filled.
• AP disappears at higher hydrogen concentrations due to a single type of carrier at the Fermi level.
• Significant modifications in screening properties of PdHx systems were observed with varying energy and hydrogen concentration.

Conclusions:

• Hydrogen absorption drastically alters palladium's dielectric and screening properties.
• The presence and disappearance of the acoustic-like plasmon are directly linked to the electronic band structure and carrier type at the Fermi level.
• These findings provide insights into the behavior of palladium hydride and its potential applications.