Electronic origin of superabundant vacancies in Pd hydride under high hydrogen pressures

TL;DR

This paper investigates how high hydrogen pressures induce superabundant vacancies in Pd hydride, revealing an electronic origin linked to valence electron energy minimization, which explains defect formation in metal hydrides.

Contribution

It introduces an electronic mechanism based on Hume-Rothery effects to explain vacancy formation in Pd hydride under high hydrogen pressures.

Findings

Vacancies form in Pd hydride at high hydrogen pressures.

Electronic effects, specifically valence electron energy minimization, drive vacancy formation.

The mechanism applies to other metal hydrides as well.

Abstract

Formation of a defect face-centered cubic structure containing metal vacancies in Ni-H and Pd-H alloys was observed experimentally at high temperature annealing under high hydrogen pressure. Appearance of vacancies in the fcc structure of the Pd hydride and several other metal hydrides can be accounted for by electronic origin assuming that valence electron energy is minimized due to Hume-Rothery effects.